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Bu tezde, gravite eşitliğinin teorik temellerini, özelliklerini ve tahmin etmekte kullanılan farklı ekonometrik yöntemler incelenmektedir. Tezde, GSYİH, uzaklık ve nüfus değişkenlerinin ECOWAS ülkelerinin dış ticaret akımlarına etkilerini analiz edebilmek için, Anderson ve Van Wincoop tarafından geliştirilen model kullanılmıştır. Tek taraflı bireysel etkiler veya uzak değer indekslerinin çok taraflı direnç etkisinin yerine kullanılması ve sıfır ticaretin iki taraflı etkilerini dikkate larak, PPML yönteminin ve Heckman model seçim sürecinin en etkin yöntem olduğunu, yansız tahminciler ürettiğini ve daha yüksek açıklama gücü gösterdiğini ortya akoyduk. Bununla birlikte, eşbütünleşme yöntemleri kullanılarak yapılan tahminler yapılan tahminler, PPML tahminleri ile Heckman model seçim sürecine benzer sonuçlar vermekte ve her ikisi de teorik beklentilerle tutarlıdır. Farklı yöntemlerle elde edilenn tahminler ararsındak tek fark, ECOWAS ülkelerinin gelişmişlik düzeyini tahmin etmeden kaynaklanmaktadır. Ortak sınır, ortak dil ve parasl birliğin etkilerini görmek amacıyla kukla değişkenler kullanıp ve modeli Heckman yöntemi ile tahmin ederek, bu niteliksel etkilerin ECOWAS ülkerinde ticaret hacmini artırıcı rol oynayabileceğini bulduk. may play a role in increasing the volume of trade in ECOWAS countries, while transport cost reduce it.Anahtar sözcükler: Gravite modeli, panel verisi yöntemleri, eşbütünleşme, ECOWAS, sıfır ticaret akımı, PPML yöntemi, Heckman seçim süreci This thesis examined the theoretical foundations of the gravitational equation, its specifications and different econometric approaches for its estimation. We adopt Anderson and Van Wincoop (2003) specification to see the effects of GDP, distance and population variables on the trade flow of ECOWAS countries. After substitution of the multilateral resistance effect by unilateral individual effects or remoteness indices, and the zero trade flows by bilateral effects, we show that the PPML method and the Heckman selection procedure remain the most efficient because they give us unbiased estimators and relatively high explanatory power. However, from the point of view of estimation by cointegration techniques, the results are similar to PPML estimation and the Heckman selection procedure and are both consistent with the theory. They only differ in predicting the level of development of ECOWAS countries. By using the Heckman estimation method to take into effects of qualitative variables such as the common border, common language and sharing a monetary union, we found that they may play a role in increasing the volume of trade in ECOWAS countries, while transport cost reduce it.Keywords: Gravity model, Panel data methods, Cointegration, ECOWAS, Zero trade flow, PPML method, Heckman selection procedure 99

Introduction : Il s'agit de determiner les profils epidemiologiques et histologiques des tumeurs submandibulaires. Methodes : Il s'agissait d'une etude retrospective et descriptive de 10 ans (1er janvier 2000 au 31 decembre 2009), realisee dans le service universitaire d'ORL de l'hopital de Fann. Etaient inclus dans cette etude tous patients porteurs d'une tumeur submandibulaire (opere ou non), confirmee par un document histologique. Resultats : Vingt-une tumeurs submandibulaires ont ete colligees. L'âge moyen des patients etait de 34,42 ans (± 14,10), avec des extremes de 2 et 55 ans. Quinze patients (71,4%) etaient de sexe feminin, soit un sex-ratio de 0,4. Les resultats histologiques etaient obtenus a partir de 4 biopsies et de 17 pieces operatoires. Dans 13 cas (61,9%) la tumeur etait benigne et dans 8 cas (38,1%) la tumeur etait maligne. L'adenome pleomorphe dans 12 cas (57,1%), le carcinome epidermoide dans 4 cas (19%) et l'adenocarcinome dans 2 cas (9,5%) etaient les types histologiques frequents. Treize (13) patients etaient porteurs d'une tumeur benigne, dont huit (8) patients etaient de sexe feminin. Huit (8) patients etaient porteurs d'une tumeur maligne. Sept patients etaient de sexe feminin. Conclusion : Cette etude sur les tumeurs submandibulaires est marquee par une predominance feminine et une frequence elevee des adenomes pleomorphes et des carcinomes epidermoides. Key words : Glande submandibulaire, tumeur, epidemiologie, histologie

Chlorinated solvents are among the most common soil and groundwater contaminants due to their widespread use as cleaning solvents or degreasing agents. Due to their physico-chemical properties, chlorinated solvents produce large-scale plumes of pollution in the groundwater. In the densely populated north western Europe, these pollution plumes often are situated under residential and urban development areas and, therefore, not easily accessible. Vapors can migrate through building slabs and affect the quality of indoor air. That is why the CityChlor project was created. It aims at improving the quality and minimizing pollution of soil and groundwater by developing an integrated approach to tackle the threats caused by contamination with chlorinated solvents in urban areas. One of the goals of the project is to define the most reliable, fast, and cost-effective techniques to detect, characterize, and delineate chlorinated solvent pollution in groundwater. In this context, passive sampling is an innovative way of sampling contaminants in groundwater in Europe, and it seems very promising. Therefore, tests are required at each country level to make regulations concerning these samplers, which will encourage consultants to use them. That is why the aim of this work was to assess the performance of 3 passive samplers to sample chlorinated solvents in groundwater and to compare the results to those obtained with the traditional groundwater sampling method, that is to say well purging prior to groundwater sampling with a pump. The pilot site chosen to conduct these experiments is an in-service facility located in France, 60 km east from Paris, in an urban area. In this factory, door locks and metal fittings have been produced since 1926 and chlorinated solvents are used to remove grease marks from metal fittings. On site, soils are composed of one layer of silty embankments (2 to 3 m) and then a sandy horizon. The water table is at around 2 m below the ground surface and it goes to 10 m deep. In order to test passive sampling, 5 dedicated water wells were installed on site. In this way, the design of the wells was totally known and passive samplers were tested in controlled conditions. One of them was screened from 2 to 8 m deep and the other ones were screened respectively from 2 to 3.5 m; 3.5 to 5 m; 5 to 6.5 m and 6.5 to 8 m. Three passive samplers were therefore tested: PDB (Polyethylene Diffusion Bags), Ceramic Dosimeters and Gore Sorber Modules. Multilevel sampling was done in the well screened from 2 to 8 m and one sampler was installed in the middle of each screened interval of the other wells. This was done for the 3 samplers tested. PDB were very easy to install and the cost of these samplers was lower than the one corresponding to the conventional method with the pump. In addition, these samplers exhibited a good reproducibility. Ceramic dosimeters were very easy to use as well, but results were not reproducible for some compounds. Some tests are still in progress to confirm this trend. For Gore Sorber Modules, the first sampling campaigns gave consistent results comparing to the pump. In general, passive samplers seemed to be very efficient to sample HVOC in groundwater and to be a good alternative to the standard method with purge and sampling with a pump.

Chlorinated solvents are amongst the most common soil and groundwater contaminants due to their widespread use as dry-cleaning solvents and as degreasing agents. Due to their physicochemical properties, they produce large scale plumes of pollution in the groundwater. In the densely populated regions, these pollution plumes are located under residential and urban development areas and therefore difficultly accessible. Vapours can migrate through building slabs into indoor air. Soil vapor migration into house, with subsequent inhalation, is often the main exposure pathway to humans at sites contaminated with volatile organic compounds (VOCs). Two approaches are commonly used for quantification of indoor concentrations: indoor gas measurement or transfer modeling from the source. Model development is relatively well advanced, but measurements for model calibration and 'validation' hardly exist in the literature. Furthermore, predictions of indoor gas concentrations from different models may vary by several orders of magnitude, depending on the application. The work presented here consists in comparing modelled results and experimental measurements on a pilot site. The pilot site is a factory, where contaminations with chlorinated solvents in groundwater and the vadose zone were observed. Before beginning the campaigns of measurements, some preliminary characterizations were carried out as screening by Cone Penetration Test and BAT sampling. Then an adequate monitoring network was performed (groundwater monitoring and soil-air monitoring wells). Measurements concerned contaminant concentrations in several media (groundwater, soil, soil air, indoor air) and fluxes at soil surface, but also key model parameters (source depth, soil and concrete characteristics and other characteristics of the building like atmospheric / soil pressure difference, ventilation rates...). The analytical modeling was performed with two transport models, one based on the equations of Johnson & Ettinger, the second based on the equations of VOLASOIL adapted for a multilayer soil. The numerical modeling was performed with COMSOL Multiphysics. COMSOL is a finite element analysis for various physics and engineering applications, especially coupled phenomena or multiphysics. Measurements have shown a complex hydro geological context and the presence of multiple contaminations (in several locations and in several dates). Comparisons between measured and modeled concentrations have shown that some building parameters have a great influence on the results and that they must be site specific determined.