MEDIUM TERM DYNAMICS IN A RATIONAL EXPECTATION MODEL WITH VINTAGE CAPITAL AND APPROPRIABILITY

In this paper, we compute a model focusing on medium term dynamics, in the line of Caballero and Hammour (1998). The main features of the model are a putty-clay production function and the bargaining between workers and firms over the rent. Although using vintage units of production is a sensible way to model the dynamics of aggregate supply, it raises many computational problems that explain why it has not been very popular in the economic literature. Indeed, with a putty-clay production function, a unit-specific wage is bargained in each vintage of production, on the basis of the expectations on the remaining lifetime of the unit. And the lifetime of each vintage unit of production is set according to the expected profitability over a long time period. Thus, any proper modelling of this type of model has often been considered as too cumbersome. This explains why the putty-clay production is barely used, and why strong additional assumptions - such as fully backward expectations - are made to turn the model more tractable.The lack of tractability of the rational expectation version of the previous kind of model is related to three main difficulties. First, it has a large number of equations and expected variables. Second, equations include a lead-structure that spans the expected lifetime of a new unit. Third, some behavioural equations are highly non-linear. Here, we provide an example showing that traditional computational restrictions can be overcome by using the stack- algorithm developed to solve large rational expectation models.Simulations are run to describe the medium term dynamics of the profit share and unemployment in four OECD countries. We extend the analysis realised by Caballero and Hammour (1998) on France. They show that shifts in unemployment benefits and firing costs in the 70Æs can explain the historical developments in capital-labour relation. In a slightly different framework, Blanchard (1999) considers other explanations related to country- specific or worldwide shocks. We investigate the relevance of the main potential explanations in the light of the contrasted macro-economic performance of the US, the UK, Germany and France over the last three decades. Moreover, contrary to Caballero and Hammour (1998), who use an iterative method to solve their model, we apply a more consistent algorithm for this type of model. We also assess the advantage of such a method by comparing the simulations run with the stack-algorithm to those obtained with the Fair-Taylor iterative method.

Precision and accuracy of fish length measurements obtained with two visual underwater methods

During the VITAL cruise in the Bay of Biscay in summer 2002, two devices for measuring the length of swimming fish were tested: 1) a mechanical crown that emitted a pair of parallel laser beams and that was mounted on the main camera and 2) an underwater auto-focus video camera. The precision and accuracy of these devices were compared and the various sources of measurement errors were estimated by repeatedly measuring fixed and mobile objects and live fish. It was found that fish mobility is the main source of error for these devices because they require that the objects to be measured are perpendicular to the field of vision. The best performance was obtained with the laser method where a video-replay of laser spots (projected on fish bodies) carrying real-time size information was used. The auto-focus system performed poorly because of a delay in obtaining focus and because of some technical problems

Evaluation of denaturing gradient gel electrophoresis (DGGE) as a method of mutation detection

The success in the isolation and characterisation of genes responsible for genetic disease, the considerable molecular heterogeneity at these loci has placed a growing emphasis on the importance of mutation detection techniques both in the coding and non-coding regions of human DNA. This thesis is principally concerned with the evaluation of one method of mutation analysis: Denaturing Gradient Gel Electrophoresis (DGGE), which has been used to identify sequence variation in three model systems: the well characterised alpha-1-antitrypsin (AAT) gene, with a range of known mutations; a segment of the Y chromosome where there is evidence for very little mutation and the Phenylalanine Hydroxylase (PAH) gene which mutated causes the autosomal recessive disorder Phenylketonuria (PKU), a disease characterised by severe mental retardation. The AAT gene was used as a test locus to evaluate the general applicability of DGGE for the detection of single base pair polymorphisms. The sequence on the Y chromosome was used to set up the computer programs associated with the technique. Subsequently the technique was used to screen for mutation in 5 exons and their splice site sequences of the PAH gene in 50 unrelated Phenylketonuria (PKU) patients. In the AAT gene, all six common point mutations were resolved. In contrast, no polymorphism was identified in the segment of Y chromosome investigated. In the PAH gene, the technique identified 10 different mutations, corresponding to 42% of affected chromosomes. Of these, three, K341R, L347F, and IVS10nt-3c-t were unique and not previously reported in the international data base. Two further sequence variants which caused no obvious alteration in the function of the PAH gene were also identified. A comparison of the efficiency of DGGE, in relation to single strand conformation polymorphism (SSCP) as a mutation detection system was also performed. Only four out of the twelve mutations identified using DGGE were resolved using SSCP analysis. Furthermore SSCP analysis did not identify any other mutations not observed in the initial DGGE screen. Overall, the study has evaluated the use of DGGE as a mutation detection system. It has resolved all the common point mutations in the AAT gene, confirmed the paucity of polymorphism in the Y chromosome and identified a number of mutations present in a South-East of England PKU population

Rome et la frontière hispanique à l'époque républicaine (IIe-Ier s. av. J.-C.)

Communication au colloque international "Empires et États nationaux en Méditerranée: la frontière entre risque et protection", Le Caire, IFAO, 6-8 juin 2004 (à paraître).Rome and the hispanic frontier during the Republic (second and first centuries BC)Les deux derniers siècles avant notre ère marquent pour Rome le moment où se redéfinit le rapport entre un centre (l'Italie) et une périphérie (les territoires provinciaux et leurs marges barbares). Les Romains conçurent-ils cette périphérie nouvelle comme une frontière ? Cette interrogation prend un relief particulier en Hispanie, théâtre d'opérations militaires continuelles depuis la seconde guerre punique jusqu'à l'effondrement du régime républicain. À la notion commode, mais impropre, de limes – encore trop fréquemment invoquée pour la péninsule Ibérique à cette époque –, doit être substituée une conception beaucoup plus large et nuancée de la « frontière » hispanique. Avant tout, l'attitude romaine était marquée au coin d'un impérialisme agressif qui faisait de cette frontière, pour les milieux dirigeants de Rome, un lieu où l'on pouvait ambitionner d'accroître son prestige militaire et, partant, d'asseoir sa légitimité politique. D'autre part, il n'était question ni d'une ligne de défense à établir face aux barbares, ni même d'une zone à défendre contre une menace d'agression éventuelle : les provinces de Citérieure et d'Ultérieure ne formaient pas un territoire dont il se serait agi de préserver à tout prix l'intégrité. Il s'agissait plutôt d'un pouvoir, exercé sur des peuples et des communautés, dont la cohérence était essentiellement politique et juridique, avant d'être territoriale. Dans ce système poreux, c'étaient les communautés locales, ou même les propriétaires de domaines agricoles, qui devaient prendre en main leur propre sécurité, comme le montre notamment la diffusion rapide du modèle architectural de la maison forte. Aussi étrange que cela puisse nous paraître, Rome bénéficiait de l'adhésion d'une grande partie des élites indigènes de l'Hispanie, convaincues de la toute puissance et de l'universalité de son Empire, alors qu'elle leur abandonnait presque entièrement la charge des risques quotidiens, inhérents à une frontière non militarisée

Response of breeding European Storm Petrels to habitat change

International audienceMainly through trampling and manuring, ground-nesting seabirds induced significant habitat changes both on vegetation cover and soil in one of the largest French colonies of European Storm Petrel , Habitat deterioration led to a high level of erosion and the collapse of many former Rabbit burrows previously occupied by breeding Storm Petrels. The loss of burrows accelerated in recent years since Great Cormorants bred on the islet with growing numbers. The main consequence of this disturbance was at first shifting of breeding Storm Petrels from burrows to rocky sites, reflecting some behavioral plasticity to buffer environmental variability. But over 18 years, a significant decrease in breeding numbers of Storm Petrels was recorded and attributed to continuous nest site destruction. Thus, other behavioral responses were also suspected, such as temporary non-breeding or emigration of birds that have to find a new nest site. Such a problem of heavy erosion and loss of nesting habitat could induce serious detrimental effects on burrowing seabirds breeding in a limited number of colonies

Angular momentum evolution can be predicted from cosmological initial conditions

The angular momentum of dark matter haloes controls their spin magnitude and orientation, which in turn influences the galaxies therein. However, the process by which dark matter haloes acquire angular momentum is not fully understood; in particular, it is unclear whether angular momentum growth is stochastic. To address this question, we extend the genetic modification technique to allow control over the angular momentum of any region in the initial conditions. Using this technique to produce a sequence of modified simulations, we can then investigate whether changes to the angular momentum of a specified region in the evolved universe can be accurately predicted from changes in the initial conditions alone. We find that the angular momentum in regions with modified initial conditions can be predicted between 2 and 4 times more accurately than expected from applying tidal torque theory. This result is masked when analysing the angular momentum of haloes, because particles in the outskirts of haloes dominate the angular momentum budget. We conclude that the angular momentum of Lagrangian patches is highly predictable from the initial conditions, with apparent chaotic behaviour being driven by stochastic changes to the arbitrary boundary defining the halo

Stellar angular momentum can be controlled from cosmological initial conditions

The angular momentum of galaxies controls the kinematics of their stars, which in turn drives observable quantities such as the apparent radius, the bulge fraction, and the alignment with other nearby structures. To show how angular momentum of galaxies is determined, we build high (35 pc) resolution numerical experiments in which we increase or decrease the angular momentum of the Lagrangian patches in the early universe. We perform cosmological zoom-in simulations of three galaxies over their histories from z = 200 to z = 2, each with five different choices for the angular momentum (15 simulations in total). Our results show that altering early universe angular momentum changes the timing and orbital parameters of mergers, which in turn changes the total stellar angular momentum within a galaxy’s virial radius in a predictable manner. Of our three galaxies, one has no large satellite at z = 2; in this case, the specific angular momentum is concentrated in the central galaxy. Our changes to the initial conditions result in its stellar angular momentum changing over 0.7 dex (from 61 to 320kpckms−1⁠) at z = 2. This causes its effective radius to grow by 40 per cent, its v/σ parameter to grow by a factor of 2.6, and its bulge fraction to decrease from 0.72 to 0.57. This proof of concept illustrates how causal studies can contribute to a better understanding of the origin of galaxy scaling relations and intrinsic alignments

Disparités institutionnelles et flexibilité des marchés du travail dans l’UE.

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Le division du sujet élève peut-elle être le lieu de travail de son écriture?

National audienceL'écrivain Perec a tenté d'échapper à la feuille blanche en utilisant la contrainte d'écriture. Pourtantil lui faudra une analyse avec Pontalis - réorganisant ainsi par la cure la division du sujet - pourretrouver l'objet du désir, en lien avec le rapport au savoir et à l'écriture.Avec ce cas, la psychanalyse nous apporte le chaînon entre la notion de sujet didactique (Reuter,Delcambre, 2007) et la didactique clinique ( Carnus, Terrisse, 2010, 2013). Situé socialement,scolairement, pris dans les relations interpersonnelles, structuré par son inconscient, l'élève est unsujet pris dans le didactique et entre en apprentissage de l'écriture avec sa complexité, sesambivalences, ses tensions. Son rapport à l'écrit et au savoir profondément attachés au désir ( Barréde Miniac 2000, Lacan 1971) tanguera au rythme des oscillations de sa division, remise sur le travailau sein de cet apprentissage .L'ingénierie didactique observant une situation d'écriture en classe tâchera de décrire et d'expliquerces mouvements

Les colloques français-breton à la croisée des rapports du français et du breton

Près de 300 ans d’existence, 75 éditions connues : lorsqu’en 1626, Guillaume Quiquer de Roscoff fit pour l’imprimeur G. Allienne de Morlaix la traduction d’un manuel de conversation issu de Flandre, il ne pouvait pas s’attendre à un tel succès. Il fut réédité presque tel quel jusqu’en 1759 à Quimper. À partir de 1717 et jusqu’en 1893, une édition concurrente était apparue qui allait supplanter définitivement l’édition de Quiquer. En 1862, Troude et Milin réaliseront un ouvrage modifié dans son contenu dont la réédition perdurera jusqu’en 1914. Enfin, une édition vannetaise dura de la fin du XVIIIe jusqu’en 1911. Il est surprenant qu’un tel monument, un phénomène social d’une telle importance, ait suscité si peu d’intérêt jusqu’à présent.Almost 300 years of existence, 75 known editions: when in 1626 Guillaume Quiquer from Roscoff translated a conversation manual from Flanders for the printer G. Allienne in Morlaix, he could not have expected such success. It was reprinted almost unchanged until 1759 in Quimper. From 1717 until 1893, a competing edition had appeared that would definitively supplant Quiquer's edition. In 1862, Troude and Milin produced a modified edition, which was reprinted until 1914. Finally, a Vannes edition lasted from the end of the 18th century until 1911. It is surprising that such a monument, a social phenomenon of such importance, has attracted so little interest to date