Heliocentric evolution of the degradation of polyoxymethylene: Application to the origin of the formaldehyde (H2CO) extended source in Comet C/1995 O1 (Hale-Bopp)

The H₂CO production rates measured in Comet C/1995 O1 (Hale-Bopp) from radio wavelength observations [Biver, N., and 22 colleagues, 2002a. Earth Moon Planets 90, 5-14] showed a steep increase with decreasing heliocentric distance. We studied the heliocentric evolution of the degradation of polyoxymethylene (formaldehyde polymers: (CH₂O)_n, also called POM) into gaseous H₂CO. POM decomposition can indeed explain the H₂CO density profile measured in situ by Giotto spacecraft in the coma of Comet 1P/Halley, which is not compatible with direct release from the nucleus [Cottin, H., Bénilan, Y., Gazeau, M.-C., Raulin, F., 2004. Icarus 167, 397-416]. We show that the H₂CO production curve measured in Comet C/1995 O1 (Hale-Bopp) can be accurately reproduced by this mechanism with a few percents by mass of solid POM in grains. The steep heliocentric evolution is explained by the thermal degradation of POM at distances less than 3.5 AU. This study demonstrates that refractory organics present in cometary dust can significantly contribute to the composition of the gaseous coma. POM, or POM-like polymers, might be present in cometary grains. Other molecules, like CO and HNC, might also be produced by a similar process.     

Water-poverty relationships in the coastal town of Mbour (Senegal): Relevance of GIS for decision support

Coastal area is always a zone with complex problems. Due to the attraction they exert, are facing many social problems. Therefore, a coastal city is usually a city with problems. Its extension, caused by the influx of people from different backgrounds, creates an increased demand for services. One of the problems frequently encountered, especially in Senegal, is access to water. The problem of access to water is poorly treated, without being correlated with the urban evolution, i.e. with increasing population and demand growth. The water resource is facing numerous complications such as the lack of integrated management, integration issues at the governance level, where the local factor is often forgotten.The town of Mbour, object of our study, does not come out of that lot, being an attractive coastal city, from an African country. This indicates the need for an integrated management oriented from local to a global basis and not vice versa. The study presented in this paper indicates that a large proportion of the population has not access to a verified drinking water system and uses water from wells or standpipes. Half of the surveyed population (50%) has no access to a water supply system. The water poverty map of the town overlaps with that of the general poverty excepting few neighborhoods. This means that even areas that are not affected by poverty have a very low or poor access to water, which so far remains the perverse effect of the reform of the Senegalese water sector in 1995.     

Mesoscale numerical modeling of meteorological events in a strong topographic gradient in the northeastern part of Mexico

A series of numerical experiments were carried out to study the effect of meteorological events such as warm and cold air masses on climatic features and variability of a understudied region with strong topographic gradients in the northeastern part of Mexico. We applied the mesoscale model MM5. We investigated the influence of soil moisture availability in the performance of the model under two representative events for winter and summer. The results showed that a better resolution in land use cover improved the agreement among observed and calculated data. The topography induces atmospheric circulation patterns that determine the spatial distribution of climate and seasonal behavior. The numerical experiments reveal regions favorable to forced convection on the eastern side of the mountain chains Eastern Sierra Madre and Sierra de Alvarez. These processes affect the vertical and horizontal structure of the meteorological variables along the topographic gradient.     

Coupling Mesoscale Modelling with a Simple Urban Model: The Lisbon Case Study

The ongoing trend of urbanisation worldwide is leading to a growing requirement for detailed flow and transport parameterisations to be included within numerical weather prediction (NWP) models. Such models often employ a simple roughness parameterisation for urban areas, which is not particularly accurate in predicting or assessing the flow and dispersion at street scale. Moreover, this kind of parameterisation offers too poor a representation of the mechanical and thermal forcing exerted by urban areas on the larger scale flow. At present, high computational costs and long simulation running times are among the constraints for the implementation of more detailed urban sub-models within NWP models. To overcome such limitations, a downscaling procedure from the atmospheric flow at the synoptic scale to the neighbourhood scale and below, is presented in this study. This is achieved by means of a simple urban model based on a parameterised formulation of the drag exerted by the building on the airflow. Application of the urban model for estimating spatially-averaged mean wind speed and the urban heat island over a selected neighbourhood area in Lisbon, Portugal, is presented. The results show the capability of the urban model to provide more accurate mean wind and temperature profiles. Moreover, the urban model has the advantage of being cost effective, as it requires small computational resources, and thus is suitable to be adopted in an operational context. The model is simple enough to be also used to assess how the resolving of urban surface processes may affect those at the larger scales.     

Spatio-temporal Variability Sea Level Pressure （SLP） the Mid-to-Low Reaches of Northern Hemipheric and Precipitation over of the Yangtze River

The spatio-temporal variability of Northern Hemisphere Sea Level Pressure （SLP） and precipitation over the mid-to-low reaches of the Yangtze River （PMLY） is analyzed jointly using the multi-taper/singular value decomposition method （MTM-SVD）. Statistically significant narrow frequency bands are obtained from the local fractional variance （LFV） spectrum. Significant interdecadal （i.e., 16-to-18-year periods） and interannual （i.e., 3-to-6-year periods） signals are identified. Moreover, a significant quasi-biennial signal is identified but only for PMLY data. The spatial joint evolution of patterns obtained for peaks in the LFV spectrum sheds light on relationships between SLP and PMLY： the Arctic Oscillation （AO） modulates the variability of the PMLY while the interannual variability of PMLY is in phase with the Northern Atlantic Oscillation （NAO） and the Northern Pacific Oscillation （NPO）.     

Duality properties of Gorringe–Leach equations

In the category of motions preserving the angular momentum direction, Gorringe and Leach exhibited two classes of differential equations having elliptical orbits. After enlarging slightly these classes, we show that they are related by a duality correspondence of the Arnold–Vassiliev type. The specific associated conserved quantities (Laplace–Runge–Lenz vector and Fradkin–Jauch–Hill tensor) are then dual reflections of each other.     

云南哈播斑岩型铜（ 钼 金）矿床地质与成矿背景研究

哈播斑岩铜(-钼-金)矿床位于哀牢山-红河新生代成矿带南端西侧,是近年来新发现的一个斑岩型矿床.矿区内出露的哈播侵入体具有多期侵入的特征,花岗岩依次侵入的序列为坪山花岗岩、三道班花岗岩、阿树花岗岩、哈播南山花岗岩(37.3 Ma),随后有4期斑岩侵入到哈播南山花岗岩中,依次为黑云母钾长石斑岩、石英钾长石斑岩、石英二长斑岩和晚期黑云母钾长石斑岩岩脉.采用LA-ICP-MS锆石U-Pb年龄法测定黑云母钾长石斑岩和石英二长斑岩的加权平均年龄分别为36.20±0.20 Ma和36.19±0.22 Ma,哈播南山花岗岩和4期斑岩具有相似的岩石地球化学特征,都有富钾、高氧化态和类似岛弧花岗岩的岩石地球化学特征,可能具有相同的来源.辉钼矿Re-Os年龄显示,哈播矿床的成矿年龄为35.47±0.16 Ma.相似的成岩-成矿年龄暗示哈播矿床成岩和成矿作用是一个连续的岩浆-热液过程,与玉龙斑岩铜矿相似.基于哈播矿床的岩石学、地球化学特点,结合前人关于青藏高原东部斑岩铜矿的研究成果,我们认为哈播斑岩矿床可能为藏东富碱斑岩带向东南的延伸,与玉龙斑岩铜矿带具有相似的成因,为哀牢山-红河新生代成矿带的重要组成部分,是晚碰撞构造转换背景下的重要产物.     

Ab initio quantum mechanical study of γ-AlOOH boehmite: structure and vibrational spectrum

The structure and vibrational spectrum of boehmite have been investigated at the quantum-mechanical level with the CRYSTAL code, using a Gaussian-type basis set and the B3LYP Hamiltonian. Three space groups are considered in this study: Cmcm, Cmc2₁, P2₁/c. Cmcm turns out to correspond to a transition state, whereas Cmc2₁ and P2₁/c are minimum energy structures. The difference among them is the position of H atoms only, the Al-O frame being essentially the same. Harmonic frequencies at the Γ point have been computed. The comparison between calculated and experimental frequencies shows a good agreement for the Al-O part of the spectrum (under 790 cm⁻¹). For the Al-OH bending modes (800–1,300 cm⁻¹) an absolute differences of 50–100 cm⁻¹ is observed; for the OH stretching modes (3,200–3,500 cm⁻¹) it increases to 120–200 cm⁻¹: anharmonicity is large because OH groups are involved in strong hydrogen bonds.     

Long-term groundwater resource observatory for Southwestern Madagascar

Madagascar has one of the highest poverty rates in the world and consequently the long-term monitoring of groundwater resources is not a priority for the authorities. However, groundwater is often the only sustainable resource that has a satisfactory quality to supply the population. This is especially true in the south-west of the country, which is a semi-arid region and a global change hot spot (intense land use and climate changes). In response to the lack of data, the Groundwater Resource Observatory for Southwestern Madagascar (GROSoM) was established to monitor piezometry and meteorology over the longer term as part of a humanitarian response. The first site was setup in 2014 in a catchment located over a carbonate plateau; in 2018, a second site was installed in an alluvial setting within a crystalline basement catchment and a third site will be installed in 2020 to monitor groundwater dynamics in a coastal setting. The three sites, located between Toliara and Taolagnaro cities, are complementary and representative of various hydrogeological systems in Southwestern Madagascar. Each site includes a weather station and between 3 and 6 piezometric probes. The monitoring data indicate a strong inter-annual variability in precipitation, which induces a strong variability in aquifers recharge. One of the driest years in 2016 seems to be consistent with strong El Niño – Southern Oscillation (ENSO) effects observed at the global scale, while years with higher recharge appear to be related to cyclones such as Fundi in 2015 and Eketsang in 2019. Preliminary results of cross-disciplinary studies demonstrated a link between groundwater and health issues (i.e., admissions to basic health centres). This observatory aims to produce long-term data and has two objectives: (i) strengthening the early warning system for humanitarian crises in Madagascar; (ii) contributing to a better understanding of the effects of climate change on groundwater resources in this semi-arid region.