The short-run dynamics of optimal growth models with delays

Differential equations with advanced and delayed time arguments may arise in the optimality conditions of simple growth models with delays. Models with investment gestation lags (time-to-build), consumption gestation lags (habit formation) or learning by using lie in this category. In this paper, we propose a shooting method to deal with leads and lags in the Euler system associated to dynamic general equilibrium models in continuous time. We introduce the discussion describing the dynamics that emerge under various assumptions on learning by using and gestation lags. Then, we implement the numerical method we propose to solve for the short run dynamics of a neoclassical growth model with a simple time to-build-lag.Time-to-build, Shooting method, DDEs.

The inequalities of change in a Greek mountain village (Sterea Hellas: Evritania)

Cet article se basesur 8 mois de travailsur le terrain effectué en 1978.dans un village montagnard d'Evritanie en Grèce Centrale.Les changements sociaux, dans la définition la plus large du terme, seproduisent sur plusieurs niveaux de l'organisation sociale: économeque, politique, social, etc... Ces niveaux sont étroitement liés entre eux dans l'univers social, quoique les changements qui les affectent soient souvent inégaux, c'est-à-dire qu'ils se produisent à des rythmesdifférents et pour les raisons variées. Ln conséquence, ceschangements peuvent entraîner certaines contradictions (par exemple l'absence de changement) dans une composante quelconque duchamp social ou dans lefonctionnement de la société en question. C eschangements peuvent également faire apparaître certaines inégalités entre diverses parties de la société, par exemple entre régions ruraleset urbaines.L'article décrit les manifestations et les raisons de l'inégalité du changement dans une communauté donnée de la Grèce rurale. Levillage, dans la société globale grecque, est souvent «défavorisé», pour la bonne raison que les changements qui s'y produisent, dépen dent, en grande partie, de processus qui dépassent ses frontières. Cecise manifeste dans certaines contradictions qui naissent au sein mêmedu village, par exemple dans la façon dont se combinent le«moderne» et le «traditionnel». On peut comprendre le village si onle considère comme le lieu où s'exercent des forces qui lui sont extérieures et à la lumière d'évènements qui sont propres à la sociétéglobale. C’est dans cette perspective que l'on peut savoir pourquoi une communauté particulière existe sous sa forme actuelleThe article is based on total of 8 months fieldwork during 1978. ina mountain village in Lvrilania. Central Greece.Social change, in its broadest definition, takes place on a number of different levels (the different aspects of social organization: economic,political, social etc.). These levels are interrelated in their widesocietal setting though the changes that occur in them are often une qual. That is, they take place at different rates and for differentreasons. They may, consequently, result in certain contradictions(such as the lack of change) at any point in the social setting or in thefunctioning of the society in question. They may also bring about certain inequalities-between different segments of society, such as ruraland urban areas.Here, the article briefly outlines manifestations of. and the reasonsfor, the inequalities of change in a particular community in CentralGreece. I wish to suggest that in the Greek social totality the village isoften «short-changed» exactly because changes in it are largelydependent on processes that go beyond its boundaries. This ismanifested in certain contradictions within the village, for. example,in the way the «modern» and the «traditional» are combined. Thevillage makes sense when seen as part of extra-village forces andevents which constitute the properties of wider society. It is in thisperspective that the question why a particular community exists inthe form it does can be assessed

Birds and people in Europe

At a regional scale, species richness and human population size are frequently positively correlated across space. Such patterns may arise because both species richness and human density increase with energy availability. If the species-energy relationship is generated through the 'more individuals' hypothesis, then the prediction is that areas with high human densities will also support greater numbers of individuals from other taxa. We use the unique data available for the breeding birds in Europe to test this prediction. Overall regional densities of bird species are higher in areas with more people; species of conservation concern exhibit the same pattern. Avian density also increases faster with human density than does avian biomass, indicating that areas with a higher human density have a higher proportion of small-bodied individuals. The analyses also underline the low numbers of breeding birds in Europe relative to humans, with a median of just three individual birds per person, and 4 g of bird for every kilogram of human

Spondylolysis and Spinal Adaptations for Bipedalism: The Overshoot Hypothesis

Background and objectives The study reported here focused on the aetiology of spondylolysis, a vertebral pathology usually caused by a fatigue fracture. The goal was to test the Overshoot Hypothesis, which proposes that people develop spondylolysis because their vertebral shape is at the highly derived end of the range of variation within Homo sapiens. Methodology We recorded 3D data on the final lumbar vertebrae of H. sapiens and three great ape species, and performed three analyses. First, we compared H. sapiens vertebrae with and without spondylolysis. Second, we compared H. sapiens vertebrae with and without spondylolysis to great ape vertebrae. Lastly, we compared H. sapiens vertebrae with and without spondylolysis to great ape vertebrae and to vertebrae of H. sapiens with Schmorl’s nodes, which previous studies have shown tend to be located at the ancestral end of the range of H. sapiens shape variation. Results We found that H. sapiens vertebrae with spondylolysis are significantly different in shape from healthy H. sapiens vertebrae. We also found that H. sapiens vertebrae with spondylolysis are more distant from great ape vertebrae than are healthy H. sapiens vertebrae. Lastly, we found that H. sapiens vertebrae with spondylolysis are at the opposite end of the range of shape variation than vertebrae with Schmorl’s nodes. Conclusions Our findings indicate that H. sapiens vertebrae with spondylolysis tend to exhibit highly derived traits and therefore support the Overshoot Hypothesis. Spondylolysis, it appears, is linked to our lineage’s evolutionary history, especially its shift from quadrupedalism to bipedalism. Lay summary: Spondylolysis is a relatively common vertebral pathology usually caused by a fatigue fracture. There is reason to think that it might be connected with our lineage’s evolutionary shift from walking on all fours to walking on two legs. We tested this idea by comparing human vertebrae with and without spondylolysis to the vertebrae of great apes. Our results support the hypothesis. They suggest that people who experience spondylolysis have vertebrae with what are effectively exaggerated adaptations for bipedalism

The Pelagic - Sargassum Ichthyofauna of the Eastern Gulf of Mexico

A total of 2857 fishes comprising 15 families and 40 species was collected at 62 localities in the eastern Gulf of Mexico between 1971 and 1976. The fauna was dominated by the Carangidae, Balistidae, and Syngnathidae. Monacanthus hispidus was the most abundant species and comprised 84.5% of the total fauna. Species diversity (H\u27) was variable within the Gulf and low in comparison with the western Atlantic Sargassum - associated ichthyofauna. Index of Affinity was high within the Gulf due to the abundance of M. hispidus. Perhaps conditions associated with community dispersal, for which M. hispidus is better adapted, permit this species to dominate this community. Additionally, species diversity differences may be due to substrate area or clumpsize

The acheulean handaxe: More like a bird's song than a beatles' tune?

The goal of this paper is to provoke debate about the nature of an iconic artifact— the Acheulean handaxe. Specifically, we want to initiate a conversation about whether or not they are cultural objects. The vast majority of archeologists assume that the behaviors involved in the production of handaxes were acquired by social learning and that handaxes are therefore cultural. We will argue that this assumption is not warranted on the basis of the available evidence and that an alternative hypothesis should be given serious consideration. This alternative hypothesis is that the form of Acheulean handaxes was at least partly under genetic control

Blowdown Simulation of CO2 Pipelines

Pipelines are the most practical option for transporting large volumes of captured CO2 to appropriate storage sites as part of the Carbon Capture and Storage (CCS) process. Proper maintenance, including periodic blowdown of pipelines or pipeline sections, is necessary for their safe operation, a pre-requisite for the public acceptance of CCS. Given the relatively high Joule-Thomson coefficient of CO2, blowdown can present significant risks to pipeline infrastructure. Depressurisation will result in rapid cooling of the inventory, potentially to below the CO2 triple point temperature (216 °K); and adjoining pipe wall, which may cool below its ductile to brittle transition temperature, resulting in a significant decrease in its resistance to brittle fracture. In this thesis a rigorous CFD model for pipeline outflow, based on the Euler equations, is coupled with a Finite Element model of heat conduction (referred to hereafter as FEM-O) in order to predict transient pipe wall temperatures during the depressurisation of CO2 pipelines. The Peng Robinson Equation of State (EoS) is selected from a range of EoS including the Soave-Redlich-Kwong, Span and Wagner and GERG 2008 for use with FEM-O. The selection was based on a review of the literature, the accepted computational efficiency of cubic EoS and a comparison of outflow predictions with large-scale experimental data generated by the UK National Grid. New formulations of two and three pipe junction boundary conditions are developed for FEM-O in order to model controlled venting of CO2 pipelines. FEM-O is validated against data gathered from various large-scale dense phase CO2 release experiments conducted by the UK National Grid. These included two full bore rupture experiments of a 144 m long, 0.15 m diameter shock tube, a pseudo-steady state release through two 0.05 m diameter pipes joined in series and the blowdown of a large CO2 pipe system through a 5.88 m long, 0.08 m diameter vertical vent pipe connected to a T-junction. One shock tube experiment utilised a binary mixture of dense phase CO2 with N2. The rest of the tests employed pure, dense phase CO2. Allowing for uncertainty in the experimental data, FEM-O predicted the range and rate of outer pipe wall cooling to ± 4 °C throughout each decompression test. Outer pipe wall temperatures were observed and predicted to fall from ambient temperatures to as low as 247 K over ca. 25 s. Fluid pressure and rapid transient predictions closely matched the experimental data. Fluid temperature was consistently under predicted by FEM-O. For the pseudo steady-state experiment, fluid pressure around the junction of the pipes was under predicted by ca. 5 bara (12 %) and fluid temperature predictions by less than 1 %. No experimental wall temperature data was recorded. For the venting of a pipeline system through a T-junction; FEM-O significantly over predicted fluid and pipe wall temperatures compared to the experimental data. This resulted from the assumption of isentropic fluid flow through the T-junction, which in this experiment caused the model to converge on an unrealistic solution for fluid entropy in the fitting. A verification study was also performed to investigate the performance of the FEM steady state pipe wall temperature calculation algorithm, the sensitivity of the pipe wall temperature predictions to the discretisation of the solution domain and to various different boundary conditions applied. Further, the performance of the newly formulated junction boundary conditions was verified. Lastly a large scale venting experiment was simulated to investigate flow regimes in the inventory. The results demonstrate the minimum requirements for the discretisation of the solution domain in order to maintain accuracy. The uninsulated boundary condition appears to under predict transient wall temperature while the insulated and buried boundary conditions display the expected performance. The new pipeline junction boundary conditions display the expected performance. The large scale venting simulation results suggest the inventory stratifies within seconds of the initiation of venting. The accuracy of FEM-O wall temperature predictions are shown to be dependent on the applicability of the fluid model to the blowdown scenario. For FBR scenarios transient pipe wall temperature predictions agree well with the available experimental data. However improvements cannot be claimed when simulating venting scenarios. The Finite Element computer code has been prepared in modular form and may be readily integrated with other blowdown models