4 results
Landscape Evolution and Human Settlement in the Iroise Sea (Brittany, France) during the Neolithic and Bronze Age
- Yvan Pailler, Pierre Stéphan, with contributions by, H. Gandois, C. Nicolas, Y. Sparfel, A. Tresset, K. Donnart, Y. Dréano, B. Fichaut, S. Suanez, C. Dupont, L. Audouard, N. Marcoux, C. Mougne, L. Salanova, F. Sellami, M.-F. Dietsch-Sellami
-
- Journal:
- Proceedings of the Prehistoric Society / Volume 80 / December 2014
- Published online by Cambridge University Press:
- 30 September 2014, pp. 105-139
- Print publication:
- December 2014
-
- Article
- Export citation
-
The Molène archipelago appears to be particularly rich in Neolithic and Bronze Age remains and an exceptional concentration of megaliths has been brought to light. Several settlements are confirmed by dry-stone structures or by shell middens. These data give precious indications on the occupation chronology of the area. Moreover they allow us, for the first time in Brittany, to reconstruct everyday life during the late Prehistoric period. A prerequisite to this reconstruction was a better understanding of the evolution of the environment during this period, which locally implies a better knowledge of paleogeographic changes related to Holocene sea-level rise as well as on floral and faunal resources.
The results obtained through paleogeographic reconstructions show that the archipelago since 4500 bc was already disconnected from the mainland. The megalithic monuments must therefore have been erected and used by islanders present on the archipelago from the middle of the 5th to the 2nd millennium bc. The distribution of the megalithic tombs reveals landscape occupation strategies which respond to both cultural choices and natural constraints. Throughout the entire period, geographic isolation has continued to increase, although it did not imply strong cultural specificities. Nevertheless, the increasing remoteness of the islands has fostered the search for livelihoods based on the intense exploitation of coastal resources. Despite their focus on the sea, these people did not neglect what inland areas could offer as evidenced by the early agro-pastoral practices in the archipelago.
Modelling waving crops using large-eddy simulation: comparison with experiments and a linear stability analysis
- S. DUPONT, F. GOSSELIN, C. PY, E. DE LANGRE, P. HEMON, Y. BRUNET
-
- Journal:
- Journal of Fluid Mechanics / Volume 652 / 10 June 2010
- Published online by Cambridge University Press:
- 15 April 2010, pp. 5-44
-
- Article
- Export citation
-
In order to investigate the possibility of modelling plant motion at the landscape scale, an equation for crop plant motion, forced by an instantaneous velocity field, is introduced in a large-eddy simulation (LES) airflow model, previously validated over homogeneous and heterogeneous canopies. The canopy is simply represented as a poroelastic continuous medium, which is similar in its discrete form to an infinite row of identical oscillating stems. Only one linear mode of plant vibration is considered. Two-way coupling between plant motion and the wind flow is insured through the drag force term. The coupled model is validated on the basis of a comparison with measured movements of an alfalfa crop canopy. It is also compared with the outputs of a linear stability analysis. The model is shown to reproduce the well-known phenomenon of ‘honami’ which is typical of wave-like crop motions on windy days. The wavelength of the main coherent waving patches, extracted using a bi-orthogonal decomposition (BOD) of the crop velocity fields, is in agreement with that deduced from video recordings. The main spatial and temporal characteristics of these waving patches exhibit the same variation with mean wind velocity as that observed with the measurements. However they differ from the coherent eddy structures of the wind flow at canopy top, so that coherent waving patches cannot be seen as direct signatures of coherent eddy structures. Finally, it is shown that the impact of crop motion on the wind dynamics is negligible for current wind speed values. No lock-in mechanism of coherent eddy structures on plant motion is observed, in contradiction with the linear stability analysis. This discrepancy may be attributed to the presence of a nonlinear saturation mechanism in LES.
Coherent structures in canopy edge flow: a large-eddy simulation study
- S. DUPONT, Y. BRUNET
-
- Journal:
- Journal of Fluid Mechanics / Volume 630 / 10 July 2009
- Published online by Cambridge University Press:
- 10 July 2009, pp. 93-128
-
- Article
- Export citation
-
Large coherent structures over vegetation canopies are responsible for a substantial part of the turbulent transfer of momentum, heat and mass between the canopy and the atmosphere. As forested landscapes are often fragmented, edge regions may be of importance in turbulent transfer. The development of coherent structures from the leading edge of a forest is investigated here for the first time. For this purpose, the turbulent flow over a clearing–forest pattern is simulated using the Advanced Regional Prediction System (ARPS). In previous studies the code has been modified so as to simulate turbulent flows at very fine scale (0.1h, where h is the mean canopy height) within and above heterogeneous vegetation canopies, using a large-eddy simulation (LES) approach. Validations have also been performed over homogeneous forest canopies and over a simple forest–clearing–forest pattern, against field and wind-tunnel measurements. Here, a schematic picture of the development of coherent eddies downstream from the leading edge of a forest is extracted from the mean vorticity components, the Q-criterion field, the cross-correlation of the wind velocity components and the length and separation length scales of coherent structures, determined by using a wavelet transform. This schematic picture shows strong similarities with the development of coherent structures observed in a mixing layer, with four different regions: (i) close to the edge, Kelvin–Helmholtz instabilities develop when a strong wind gust hits the canopy; (ii) these instabilities roll over to form transverse vortices from around 3h downstream from the edge, characterized by a length scale close to the depth of the internal boundary layer that develops from the canopy edge; (iii) secondary instabilities destabilize these rollers and increase the vertical and streamwise vorticity components from around 6h, and two counter-rotating streamwise vortices appear; (iv) at about 9h the initial rollers have become complex three-dimensional coherent structures, with spatially constant mean length and separation length scales. These four stages of development occur closer to the edge with increasing canopy density. While this average picture of the development of coherent structures is similar to that observed in a mixing layer, the analysis of instantaneous fields shows that coherent structures behind the leading edge appear as resulting from the ‘branching’ of tubes localized in regions of low pressure, where their cores are characterized by high values of enstrophy and Q-criterion.
Long-term outcome of anorexia nervosa in a prospective 21-year follow-up study
- B. LÖWE, S. ZIPFEL, C. BUCHHOLZ, Y. DUPONT, D. L. REAS, W. HERZOG
-
- Journal:
- Psychological Medicine / Volume 31 / Issue 5 / July 2001
- Published online by Cambridge University Press:
- 12 July 2001, pp. 881-890
-
- Article
- Export citation
-
Background. Given our poor understanding of the very long-term course of anorexia nervosa, many questions remain regarding the potential for recovery and relapse. The purpose of the present study was to investigate long-term outcome and prognosis in an anorexic sample 21 years after the initial treatment.
Method. A multidimensional and prospective design was used to assess outcome in 84 patients 9 years after a previous follow-up and 21 years after admission. Among the 70 living patients, the follow-up rate was 90%. Causes of death for the deceased patients were obtained through the attending physician. Predictors of a poor outcome at the 21-year follow-up were selected based on the results of a previous 12-year follow-up of these patients.
Results. Fifty-one per cent of the patients were found to be fully recovered at follow-up, 21% were partially recovered and 10% still met full diagnostic criteria for anorexia nervosa. Sixteen per cent were deceased, due to causes related to anorexia nervosa. The standardized mortality rate was 9·8. The three groups also showed significant differences in psychosocial outcome. A low body mass index and a greater severity of social and psychological problems were identified as predictors of a poor outcome.
Conclusions. Recovery is still possible for anorexic patients after a period of 21 years. On the other hand, patients can relapse, becoming symptomatic again despite previously achieving recovery status. Only a few patients classified as having a poor outcome were found to seek any form of treatment, therefore, it is recommended that these patients should be monitored regularly and offered treatment whenever possible.