Conditional Moment Models under Semi-Strong Identification

We consider models defined by conditional moment restrictions under semi-strong identification. Identification strength is directly defined through the conditional mo- ments that flatten as the sample size increases. The framework allows for different iden- tification strengths across parameter’s components. We propose a minimum distance estimator that is robust to semi-strong identification and does not rely on the choice of a user-chosen parameter, such as the number of instruments or any other smoothing parameter. Our method yields consistent and asymptotically normal estimators of each parameter’s components. Heteroskedasticity-robust inference is possible through Wald testing without prior knowledge of the identification pattern. In simulations, we find that our estimator is competitive with alternative estimators based on many instruments. In particular, it is well-centered with better coverage rates for confidence intervals.Asset Markets, Uncertainty, Experimental Economics

Temporal patterns in the upstream migration of European eels (Anguilla anguilla) at the Couesnon estuarine dam

The temporal migration patterns of European glass eel Anguilla anguilla at the Couesnon estuarine dam (Mont-Saint-Michel Bay, France)were examined in winter and spring 2004 and 2005. The dam which is located close to the river mouth constitutes a major obstacle for upstreammigrating glass eels. The migration was observed at different temporal scales, from within individual tides to complete tidal cycles between successive spring tides. The maximum number of glass eels arrived downstream of the dam at the beginning and in the middle of the flood tide. Glass eels migrated through the dam openings preferentially from the middle of the flood to the beginning of the ebb tide. Eel densities were highest during the second tide of each tide cycle that arrived at the estuarine dam and when the difference in water level between upstream and downstream of the dam was greatest, particularly at the end of the flood. Analysis of the influence of each environmental factor provided a good prediction of the glass eel recruitment peaks and, therefore, of the most favourable temporal windows for their migration. The water level and temperature were the most important environmental factors. These results provide the information needed for a dam-management program that is compatible with glass eel migration

Study of the spatial and temporal coherence of high order harmonics

We apply the theory of high-order harmonic generation by low-frequency laser fields in the strong field approximation to the study of the spatial and temporal coherence properties of the harmonics. We discuss the role of dynamically induced phases of the atomic polarization in determining the optimal phase matching conditions and angular distributions of harmonics. We demonstrate that the phase matching and the spatial coherence can be controlled by changing the focusing parameters of the fundamental laser beam. Then we present a detailed study of the temporal and spectral properties of harmonics. We discuss how the focusing conditions influence the individual harmonic spectra and time profiles, and how the intensity dependence of the dynamically induced phase leads to a chirp of the harmonic frequency. This phase modulation can be used to control the temporal and spectral properties of the harmonic radiation. Temporally, the harmonic chirped pulse can be recompressed to very small durations. Spectrally, chirping of the fundamental beam may be employed to compensate for the dynamically induced chirp and to control the individual harmonic spectrum. Finally, we discuss the short pulse effects, in particular nonadiabatic phenomena and the possibility of generating attosecond pulses.Comment: Latex file with 37 pages, 25 postscript figures. to appear in Advances in Atomic, Molecular and Optical Physic

European eel (Anguilla anguilla): prediction of spawner escapement from continental population parameters

This paper describes the assessment of silver European eel (Anguilla anguilla) escapement based on a “sedentary” population fraction analysis in a 60-km2 watershed of northern Brittany (France). Downstream migration fluxes were monitored using eel traps and related to environmental factors. Intensive electrofishing and fyke-net fishing were conducted to assess eel biomass, densities, and population structure. A total of 564 eels, including 81 silver eels, were PIT tagged. In 1996, 616 eels were caught in the catchment including 68 silver eels (11%). During the following downstream migration period, 12 of the PIT-tagged silver eels, among a total of 678, were recaptured in the downstream traps. Seven were recaptured in the catchment in 1997. It was shown that (i) only about 20% of the silver eels present in the catchment emigrated during the following year, (ii) 12% stayed in the catchment including two (3.4%) that recovered yellow eel characteristics, and (iii) the other eels either died or settled in the catchment but were not recaptured. It was also estimated that 2% (650 eels) of the population (34 000 eels) among 3000 silver eels considered “emigration candidates” emigrated each year

Sol–gel synthesis and characterization of barium (magnesium) aluminosilicate glass sealants for solid oxide fuel cells

Solid oxide fuel cells (SOFC) correspond to efficient energy conversion systems coupled with low emissions of pollutants. In the aim to fabricate high temperature planar SOFC, glass and glass-ceramic sealants are developed to associate several criteria and properties : high thermal expansion (11.0 to 12.0 ⋅ 10− 6 K− 1), high electrical resistance > 2 kΩ/cm2, good thermochemical compatibility with the other active materials of the fuel cell, and stability under H2 and H2O atmospheres at an operation temperature of 800 °C for a long time. According to these requirements, new BAS (BaO–Al2O3–SiO2) and BMAS (BaO–MgO–Al2O3–SiO2) glass-ceramic sealants have been developed by sol–gel route which is a non-conventional process for such applications. By this soft chemistry process, we anticipate a decrease in the glasses processing temperature due to a better homogeneity between cationic precursors in the mixture and a more important reactivity of materials. Experimental results in terms of thermomechanical properties, thermal expansion coefficient, crystalline phase content, and microstructure were discussed. In particular, the influence of the %BaO on the thermomechanical properties of glass-ceramics was described. Changes in properties of glass-ceramics were closely related to the microstructure. The influence of MgO on glass processing temperatures, on the structure and on the microstructure is evaluated in order to confirm that these glass-ceramics are promising candidates to SOFC applications. So, after performing a systematic investigation to the various systems, the properties of suitable glass were proposed

Spatial distribution of an eel population (Anguilla anguilla L.) in a small coastal catchments of northern Brittany (France). Consequences hydraulic works.

The Frémur is a 60 km2 catchment of Brittany where many hydraulic works (dams, weirs, gauging structures, etc.) have reduced the recruitment by elvers and glass eels since at least 50 years. In 1992, an eel lift was built on the main dam (14 m high) and in 1996, two other dams (5 m high) located downstream were equipped with eel passes to improve upstream migration. In 1995, before the construction of the passes, eel population parameters (density, biomass and size distribution) were assessed at the scale of the whole watershed by electrofishing (removal method) in 33 stations. The average biomass was high (19 g/m2 ) despite the numerous physical obstructions. However, there was an accumulation of eels downstream many hydraulic works and very low densities immediately upstream. Moreover, downstream the first obstruction, at 2 km from the sea, the population is dominated by boot lace eels and elvers (< 100 mm), whereas this size class is absent in upstream reaches. These results suggest that the standing capacity of the watershed is not reached and that the population could be enhanced in the next years by the recently installed eel passes

Conditional Moment Models under Weak Identification

We consider models defined by a set of conditional moment restrictions where weak identification may arise. Weak identification is directly defined through the conditional moments that are allowed to flatten as the sample size increases. We propose a minimum distance estimator of the structural parameters that is robust to potential weak identification and that uses neither instrumental variables nor smoothing. Hence, its properties only depend upon identification weakness, and not on the interplay between some tuning parameter, as the growth rate of the number of instruments, and the unknown degree of weakness. Our estimator is consistent and asymptotically normal, and its rate of convergence is the same as competing estimators based on many weak instruments. Heteroskedasticity-robust inference is possible through Wald testing without prior knowledge of the identification pattern. In simulations, we find that our estimator is competitive with estimators based on many instruments

Traces of strong selective pressures in the genomes of C 4 grasses

C4 photosynthesis is nature’s response to CO2 limitations, and evolved recurrently in several groups of plants. To identify genes related to C4 photosynthesis, Huang et al. looked for evidence of past episodes of adaptive evolution in the genomes of C4 grasses. They identified a large number of candidate genes that evolved under divergent selection, indicating that, besides alterations to expression patterns, the history of C4 involved strong selection on protein-coding sequences

Analyse des interactions agressives dans le football Beninois : Aspects spatiaux et temporels

La présente étude procède d'une analyse des interactions agressives dans le football béninois dans ses aspects spatiaux et temporels. Elle concerne&nbsp; 12 équipes évoluant dans le championnat de football de première division nationale lors de 24 rencontres jouées à domicile et sur terrain adverse.&nbsp; Sur la base de la classification de Pfister, 2465 interactions agressives ont été enregistrées dont 59,36% lors des rencontres jouées à domicile contre&nbsp; 40,64% sur terrain adverse. Aussi bien à domicile qu'à l'extérieur, les résultats révèlent que c'est la zone médiane (milieu de terrain) qui enregistre le&nbsp; plus d'interactions agressives (46,70%) que celle de l'attaque (33,51%) qui est supposée zone sensible d'interactions agressives. En outre, ces&nbsp; interactions surviennent pour la majorité (60,69%) dans la 2ème mi-temps des rencontres, ce qui rejoint les résultats des travaux réalisés par Pfister,&nbsp; en ce qui concerne le comportement des footballeurs français de première division en matière d'interactions agressives. Les données enregistrées&nbsp; montrent qu'il n'existe pas de différence significative dans les comportements agressifs entre les footballeurs français et béninois. &nbsp; The current study&nbsp; proceeds from an analysis of aggressive interactions in the Beninese football on its space and temporal aspects. It concerns 12 teams&nbsp; evolving in the soccer first division championship during 24 games played at home and on the adverse field. On the basis of Pfister's (1985)&nbsp; classification, 2465 aggressive interaction have been recorded, of which 59.36% during the games played at home versus 40.64% on the adverse&nbsp; field. The results show that, as well at home as outside, the middle of the field is the area where more aggressive interactions (46.70%) are recorded&nbsp; than that of the attack (33.55%) which is supposed to be the sensitive area of aggressive interactions. Moreover, the greatest part of those&nbsp; interactions (60.69%) occurs in the second half-time of matches, which goes back to the results of the researches carried out by Pfister (1986) on&nbsp; aggressive interactions as far as the behavior of the French football players of the first division is concerned. These relevant data show that it does&nbsp; not exist any significant difference on the aggressive behaviors between the French and the Beninese football players.&nbsp