Contribution de la Régénération Naturelle Assistée des ligneux dans l’approvisionnement en bois des ménages dans le département de Magaria (Niger)

Cet article présente les impacts de la Régénération Naturelle Assistée (RNA) sur l’approvisionnement en bois des ménages dans deux terroirs villageois (Arasofoua et Gaounawa) du département de Magaria au Niger. L’objectif visé était d’évaluer la quantité de bois utilisée au niveau des ménages pour les différents usages (bois énergie, construction, et service). La méthodologie utilisée pour atteindre cet objectif a consisté en des enquêtes auprès des ménages sur le type de bois utilisé et leur quantité ainsi que des mesures pour évaluer le changement induit à travers la pratique de la Régénération Naturelle Assistée. Les résultats obtenus montrent que les populations de ces villages arrivent à satisfaire leurs besoins en bois de feu et de service. Cette technique est pratiquée depuis 1994 dans ces villages. Chaque exploitant collecte en moyenne 24,9 et 17,5 m³ de bois par an dans les deux terroirs villageois respectivement en fonction des différents types d’usage (chauffe, construction, ustensiles de cuisine, etc.) et types de bois utilisés. Environ 90,8% des exploitants n’achètent pas le bois. L’autoconsommation moyenne en bois dans les deux villages est de 57,8%. Les transhumants et les coupes frauduleuses, constituent les contraintes majeures de cette pratique. Sensibiliser et former davantage les paysans aux techniques de régénération et impliquer les femmes dans cette nouvelle pratique favoriseraient la constitution de parcs agroforestiers.Mots clés: Innovation, ménages, produits ligneux, Sahel, Nige

Spitzer 3.6 micron and 4.5 micron full-orbit lightcurves of WASP-18

We present new lightcurves of the massive hot Jupiter system WASP-18 obtained with the Spitzer spacecraft covering the entire orbit at 3.6 micron and 4.5 micron. These lightcurves are used to measure the amplitude, shape and phase of the thermal phase effect for WASP-18b. We find that our results for the thermal phase effect are limited to an accuracy of about 0.01% by systematic noise sources of unknown origin. At this level of accuracy we find that the thermal phase effect has a peak-to-peak amplitude approximately equal to the secondary eclipse depth, has a sinusoidal shape and that the maximum brightness occurs at the same phase as mid-occultation to within about 5 degrees at 3.6 micron and to within about 10 degrees at 4.5 micron. The shape and amplitude of the thermal phase curve imply very low levels of heat redistribution within the atmosphere of the planet. We also perform a separate analysis to determine the system geometry by fitting a lightcurve model to the data covering the occultation and the transit. The secondary eclipse depths we measure at 3.6 micron and 4.5 micron are in good agreement with previous measurements and imply a very low albedo for WASP-18b. The parameters of the system (masses, radii, etc.) derived from our analysis are in also good agreement with those from previous studies, but with improved precision. We use new high-resolution imaging and published limits on the rate of change of the mean radial velocity to check for the presence of any faint companion stars that may affect our results. We find that there is unlikely to be any significant contribution to the flux at Spitzer wavelengths from a stellar companion to WASP-18. We find that there is no evidence for variations in the times of eclipse from a linear ephemeris greater than about 100 seconds over 3 years.Comment: 17 pages, 10 figures. Accpeted for publication in MNRA

The Interiors of Giant Planets: Models and Outstanding Questions

We know that giant planets played a crucial role in the making of our Solar System. The discovery of giant planets orbiting other stars is a formidable opportunity to learn more about these objects, what is their composition, how various processes influence their structure and evolution, and most importantly how they form. Jupiter, Saturn, Uranus and Neptune can be studied in detail, mostly from close spacecraft flybys. We can infer that they are all enriched in heavy elements compared to the Sun, with the relative global enrichments increasing with distance to the Sun. We can also infer that they possess dense cores of varied masses. The intercomparison of presently caracterised extrasolar giant planets show that they are also mainly made of hydrogen and helium, but that they either have significantly different amounts of heavy elements, or have had different orbital evolutions, or both. Hence, many questions remain and are to be answered for significant progresses on the origins of planets.Comment: 43 pages, 11 figures, 3 tables. To appear in Annual Review of Earth and Planetary Sciences, vol 33, (2005

The developmental onset of symbolic approximation: beyond nonsymbolic representations, the language of numbers matters

Symbolic (i.e., with Arabic numerals) approximate arithmetic with large numerosities is an important predictor of mathematics. It was previously evidenced to onset before formal schooling at the kindergarten age (Gilmore et al., 2007) and was assumed to map onto pre-existing nonsymbolic (i.e., abstract magnitudes) representations. With a longitudinal study (Experiment 1), we show, for the first time, that nonsymbolic and symbolic arithmetic demonstrate different developmental trajectories. In contrast to Gilmore et al.’s (2007) findings, Experiment 1 showed that symbolic arithmetic onsets in grade 1, with the start of formal schooling, not earlier. Gilmore et al. (2007) had examined English-speaking children, whereas we assessed a large Dutch-speaking sample. The Dutch language for numbers can be cognitively more demanding, for example, due to the inversion property in numbers above 20. Thus, for instance, the number 48 is named in Dutch “achtenveertig” (eight and forty) instead of “forty eight.” To examine the effect of the language of numbers, we conducted a cross-cultural study with English- and Dutch-speaking children that had similar SES and math achievement skills (Experiment 2). Results demonstrated that Dutch-speaking kindergarteners lagged behind English-speaking children in symbolic arithmetic, not nonsymbolic and demonstrated a working memory overload in symbolic arithmetic, not nonsymbolic. Also, we show for the first time that the ability to name two-digit numbers highly correlates with symbolic approximate arithmetic not nonsymbolic. Our experiments empirically demonstrate that the symbolic number system is modulated more by development and education than the nonsymbolic system. Also, in contrast to the nonsymbolic system, the symbolic system is modulated by language

An Analyses of Onion Marketing in Toro District of Toro Local Government Area in Bauchi State, Nigeria

The broad objective of the study was to determine the profitability and marketing efficiency of onion marketing in Toro District of Toro local government area in Bauchi State. Questionaire was the main instrument of data collection from a sample of fourty (40) onion traders in the study area. Analytical tools used were; descriptive statistics, gross margin, marketing margin and market efficiency. Majority (67.5%) of the respondents were males. Also, majority (55%) of onion Traders falls within the age bracket of 41 - 50 years of age, the result indicates high proportions (85.00%) of the respondents were educated. The years of Onion marketing experience of the respondents indicates that half of the respondents (50%) had 11 - 20 years of marketing experience in onion trading and the study also indicates that majority (52.50%) went into onions marketing with money between ₦21,000:00 - ₦30,000:00. Greater proportion (87.50%) of the respondents belongs to cooperative associations. Major problems of onion marketing identified were those of transportation, storage facilities, starting capital, market information and low price. Result of the costs and returns analysis revealed that onion marketing was profitable to the turn of N1,315.00 per bag for wholesale and N2,020.00 per bag for retail traders of onion marketers respectively. This finding also indicated that marketing of onion is efficient with total efficiency of 141.28% for wholesalers and 150.80% for retailers. Proper functional programmes and policies should be made to improve onion production and marketing in the study area

Understanding the atmospheric properties and chemical composition of the ultra-hot Jupiter HAT-P-7b II. Mapping the effects of gas kinetics

Funding: Part of this work was supported by the German Deutsche Forschungsgemeinschaft, DFG project number Ts 17/2–1.Aims. The atmospheres of ultra-hot Jupiters (UHJs) are commonly considered to be at thermochemical equilibrium. We aim to provide disequilibrium chemistry maps for a global understanding of the chemistry in the atmosphere of HAT-P-7b and assess the importance of disequilibrium chemistry on UHJs. Methods. We applied a hierarchical modeling approach using 97 1D atmospheric profiles from a 3D general circulation model of HAT-P-7b. For each atmospheric 1D profile, we evaluated our kinetic cloud formation model consistently with the local gas-phase composition in chemical equilibrium. This served as input to study the quenching of dominating CHNO-binding molecules. We evaluated quenching results from a zeroth-order approximation in comparison to a kinetic gas-phase approach. Results. We find that the zeroth-order approach of estimating quenching points agrees well with the full gas-kinetic modeling results. However, it underestimates the quenching levels by about one order of magnitude at high temperatures. Chemical disequilibrium has the greatest effect on the nightside and morning abundance of species such as H, H2O, CH4, CO2, HCN, and all CnHm molecules; heavier CnHm molecules are more affected by disequilibrium processes. The CO abundance, however, is affected only marginally. While dayside abundances also notably change, those around the evening terminator of HAT-P-7b are the least affected by disequilibrium processes. The latter finding may partially explain the consistency of observed transmission spectra of UHJs with atmospheres in thermochemical equilibrium. Photochemistry only negligibly affects molecular abundances and quenching levels. Conclusions. In general, the quenching points of the atmosphere of HAT-P-7b are at much lower pressures than in the cooler hot-jupiters. We propose several avenues to determining the effect of disequilibrium processes on UHJs that are in general based on abundance and opacity measurements at different local times. It remains a challenge to completely disentangle this from the chemical effects of clouds and that of a primordial nonsolar abundance.Publisher PDFPeer reviewe

Species diversity and distribution of ruderal flora on landfills in Maradi city, Niger

Waste management continues to be a critical environmental issue in cities. It impacts on the well being of the population, the environment and the biodiversity. In the city of Maradi, in Niger, more interest is given to the problem in order to understand the whole waste management system. It is in this context that this study is carried out to investigate on the role of ruderal flora on the municipal solid wastes dumpsites and landfill sites in Maradi city. The specific objectives are to determine the floristic diversity and distribution of ruderal flora on the municipal solid waste disposal sites, and to identify potential species that can play an important role in the phytoremediation of these sites. In total, 65 species belonging to 52 genera and 24 families were recorded. These species can be categorised into two groups containing anthropic and nitrophilic species according to the ascending Hierarchical Classification (AHC) at 25% similarity. Characteristic species of the first group G1 are Amaranthus viridis and Cucurbita pepo, and Datura innoxia and Cucumis melo for the second group G2. Other ruderal species, namely Amaranthus spinosus L., Amaranthus viridis L., Celosia trygina L., Datura innoxia Mill., and an introduced woody species, Cuphea hyssopifolia Kunth., found are not included in the Maradi city list of species. Datura innoxia, Amaranthus viridis and Amaranthus spinosus are species known to tolerate different degrees of pollution and their ecology should be further study to better understand how they can be used for phytoremediation on this kind of sites

Effect of structural defects on anomalous ultrasound propagation in solids during second-order phase transitions

The effect of structural defects on the critical ultrasound attenuation and ultrasound velocity dispersion in Ising-like three-dimensional systems is studied. A field-theoretical description of the dynamic effects of acoustic-wave propagation in solids during phase transitions is performed with allowance for both fluctuation and relaxation attenuation mechanisms. The temperature and frequency dependences of the scaling functions of the attenuation coefficient and the ultrasound velocity dispersion are calculated in a two-loop approximation for pure and structurally disordered systems, and their asymptotic behavior in hydrodynamic and critical regions is separated. As compared to a pure system, the presence of structural defects in it is shown to cause a stronger increase in the sound attenuation coefficient and the sound velocity dispersion even in the hydrodynamic region as the critical temperature is reached. As compared to pure analogs, structurally disordered systems should exhibit stronger temperature and frequency dependences of the acoustic characteristics in the critical region.Comment: 7 RevTeX pages, 4 figure