Four essays on economic geography, trade and development

RESUME Cette thèse se situe à la frontière de la recherche en économie du développement et du commerce international et vise à intégrer les apports de l'économie géographique. Le premier chapitre s'intéresse aux effets de création et de détournement de commerce au sein des accords régionaux entre pays en développement et combine une approche gravitaire et une estimation non paramétrique des effets de commerce. Cette analyse confirme un effet de commerce non monotone pour six accords régionaux couvrant l'Afrique, l'Amérique Latine et l'Asie (AFTA, CAN, CACM, CEDEAO, MERCO SUR et SADC) sur la période 1960-1996. Les accords signés dans les années 90 (AFTA, CAN, MERCOSUR et SADC) semblent avoir induis une amélioration du bien-être de leurs membres mais avec un impact variable sur le reste du monde, tandis que les accords plus anciens (CEDEAO et CACM) semblent montrer que les effets de commerce et de bien-être se réduisent pour finir par s'annuler à mesure que le nombre d'années de participation des Etats membres augmente. Le deuxième chapitre pose la question de l'impact de la géographie sur les échanges Sud-Sud. Ce chapitre innove par rapport aux méthodes classiques d'estimation en dérivant une équation de commerce à partir de l'hypothèse d'Armington et en intégrant une fonction de coût de transport qui prend en compte la spécificité des pays de l'UEMOA. Les estimations donnent des effets convaincants quant au rôle de l'enclavement et des infrastructures: deux pays enclavés de l'UEMOA commercent 92% moins que deux autres pays quelconques, tandis que traverser un pays de transit au sein de l'espace UEMOA augmente de 6% les coûts de transport, et que bitumer toutes les routes inter-Etat de l'Union induirait trois fois plus de commerce intra-UEMOA. Le chapitre 3 s'intéresse à la persistance des différences de développement au sein des accords régionaux entre pays en développement. Il montre que la géographie différenciée des pays du Sud membres d'un accord induit un impact asymétrique de celui-ci sur ses membres. Il s'agit d'un modèle stylisé de trois pays dont deux ayant conclu un accord régional. Les résultats obtenus par simulation montrent qu'une meilleure dotation en infrastructure d'un membre de l'accord régional lui permet d'attirer une plus grande part industrielle à mesure que les coûts de transport au sein de l'accord régional sont baissés, ce qui conduit à un développement inégal entre les membres. Si les niveaux d'infrastructure domestique de transport sont harmonisés au sein des pays membres de l'accord d'intégration, leurs parts industrielles peuvent converger au détriment des pays restés hors de l'union. Le chapitre 4 s'intéresse à des questions d'économie urbaine en étudiant comment l'interaction entre rendements croissants et coûts de transport détermine la localisation des activités et des travailleurs au sein d'un pays ou d'une région. Le modèle développé reproduit un fait stylisé observé à l'intérieur des centres métropolitains des USA: sur une période longue (1850-1990), on observe une spécialisation croissante des centres urbains et de leurs périphéries associée à une évolution croissante puis décroissante de la population des centres urbains par rapport à leurs périphéries. Ce résultat peut se transférer dans un contexte en développement avec une zone centrale et une zone périphérique: à mesure que l'accessibilité des régions s'améliore, ces régions se spécialiseront et la région principale, d'abord plus importante (en termes de nombre de travailleurs) va finir par se réduire à une taille identique à celle de la région périphérique.

Balance nutricional y número de hojas como variables de predicción del rendimiento del plátano Hartón

El objetivo de este trabajo fue desarrollar una ecuación de regresión que permitiese estimar el rendimiento (Y) del plátano Hartón (Musa AAB subgrupo plátano cv. Hartón), con la relación entre el Índice de Balance de Nutrientes DRIS (IBN-DRIS) (X1) y el número de hojas de la planta madre (X2). Usando un muestreo completamente al azar, se colectaron 398 muestras de tejido foliar. Se obtuvo la ecuación: Y = 30,351** - 8,644** log X1 + 0,27502*X2, con R² de 0,6206***, con distribución normal de los residuos. Pudo demostrarse que con la misma se puede predecir el rendimiento potencial de cualquier plantación del plátano Hartón en el área de estudio.

Urea and sugarcane straw nitrogen balance in a soil-sugarcane crop system

The objectives of this study were to evaluate nitrogen utilization by sugarcane ratoon from two sources, applied urea and sugarcane straw covering soil surface (trash blanket), besides the recovery of N from both sources in the soil-plant system. The following treatments were established in a randomized block design with four replicates: T1, vinasse-urea (100 kg ha-1 of urea-N) mixture applied on the total area of the soil covered with cane trash labeled with 15N; T2, vinasse-urea mixture (urea labeled with 15N; 100 kg ha-1 of urea-N) applied on the total area of the soil covered with non-labeled sugarcane trash; and T3, urea-15N (100 kg ha-1 of urea-N) applied in furrows at both sides of cane rows, with previous surface application of vinasse, onto soil without trash covering. The vinasse was applied at a rate of 100 m³ ha-1 in all treatments. The experiment was carried out on a Yellow Red Podzolic soil (Paleudalf), from October 1997 to August 1998, in Piracicaba, SP, Brazil. The nitrogen use efficiency of urea by the sugarcane ratoon was 21%, while that of the sugarcane straw was 9%. The main contributions of N from sugarcane trash, during one cycle, are the preservation and increase of the organic N in soil. The tendency for a lower accumulation of urea-N in the sugarcane plant, in the soil surface covered with sugarcane residue, was compensated by the assimilation of N from trash mineralization. Nitrogen derived from cane trash was more available to plants in the second half of the ratoon cycle

Increased alpha activity and modulations of fronto-parietal balance during motor transitions in the elderly

A hallmark of aging is the sensorimotor deficit, characterized by an increased reaction time and a reduction of motor abilities. Some mechanisms such as motor inhibition deteriorate with aging because of neuronal density alterations and modifications of connections between brain regions. These deficits may be compensated throughout a recruitment of additional areas. Studies have shown that old adults have increased difficulty in performing bimanual coordination tasks compared with young adults. In contrast, motor switching is poorly documented and is expected to engage increasing resources in the elderly. The present study examines performances and electro-cortical correlates of motor switching in young and elderly adults.

El marmor de Tarraco. Explotació, utilització i comercialització de la pedra de Santa Tecla en època romana Tarraco marmor. The Quarrying, Use and Trade of Santa Tecla Stone in Roman Times

Aquest és el llibre més complet que hi ha sobre la pedra de Santa Tecla i el llisós, dos materials procedents de Tarragona i molt utilitzats en època romana. Els autors, arqueòlegs i geòlegs, caracteritzen aquestes dues varietats i presenten el panorama de les seves aplicacions, i també donen pautes per identificar-les i diferenciar-les d’altres pedres que s’hi podrien confondre, com la “portasanta” o la pedra de Buixcarró.

Concept of fat balance in human obesity revisited with particular reference to de novo lipogenesis.

The measurement of fat balance (fat input minus fat output) involves the accurate estimation of both metabolizable fat intake and total fat oxidation. This is possible mostly under laboratory conditions and not yet in free-living conditions. In the latter situation, net fat retention/mobilization can be estimated based on precise and accurate sequential body composition measurements. In case of positive balance, lipids stored in adipose tissue can originate from dietary (exogenous) lipids or from nonlipid precursors, mainly from carbohydrates (CHOs) but also from ethanol, through a process known as de novo lipogenesis (DNL). Basic equations are provided in this review to facilitate the interpretation of the different subcomponents of fat balance (endogenous vs exogenous) under different nutritional circumstances. One difficulty is methodological: total DNL is difficult to measure quantitatively in man; for example, indirect calorimetry only tracks net DNL, not total DNL. Although the numerous factors (mostly exogenous) influencing DNL have been studied, in particular the effect of CHO overfeeding, there is little information on the rate of DNL in habitual conditions of life, that is, large day-to-day fluctuations of CHO intakes, different types of CHO ingested with different glycemic indexes, alcohol combined with excess CHO intakes, etc. Three issues, which are still controversial today, will be addressed: (1) Is the increase of fat mass induced by CHO overfeeding explained by DNL only, or by decreased endogenous fat oxidation, or both? (2) Is DNL different in overweight and obese individuals as compared to their lean counterparts? (3) Does DNL occur both in the liver and in adipose tissue? Recent studies have demonstrated that acute CHO overfeeding influences adipose tissue lipogenic gene expression and that CHO may stimulate DNL in skeletal muscles, at least in vitro. The role of DNL and its importance in health and disease remain to be further clarified, in particular the putative effect of DNL on the control of energy intake and energy expenditure, as well as the occurrence of DNL in other tissues (such as in myocytes) in addition to hepatocytes and adipocytes.

Transpiration stimulée afin d'améliorer l'équilibre hydro-sodé chez les patients hémodialysés : à propos d'un cas [Stimulated sweating in order to improve the water-and-salt balance in hemodialysis patients. A case report].

Obtaining the desired dry weight in dialysis patients is challenging once residual diuresis has disappeared, considering the trend of increasing dietary salt intake and shortening dialysis time over the last 40 years. We describe the case of a 55-year-old patient of Sudanese origin, who presented excessive interdialytic weight gain and hypertension on maintenance hemodialysis. After failure of conservative measures, a therapy of daily hot water baths of 30minutes each on non-dialysis days was introduced. All clinical parameters improved, including potassium profile. In this article, we review the history, pathophysiological mechanisms, efficacy and possible side effects of this interesting, somewhat forgotten technique.

Energy balance measurements over a banana orchard in the Semiarid region in the Northeast of Brazil

The objective of this work was to evaluate the reliability of eddy covariance measurements, analyzing the energy balance components, evapotranspiration and energy balance closure in dry and wet growing seasons, in a banana orchard. The experiment was carried out at a farm located within the irrigation district of Quixeré, in the Lower Jaguaribe basin, in Ceará state, Brazil. An eddy covariance system was used to measure the turbulent flux. An automatic weather station was installed in a grass field to obtain the reference evapotranspiration (ET0) from the combined FAO-Penman-Monteith method. Wind speed and vapor pressure deficit are the most important variables on the evaporative process in both growing seasons. In the dry season, the heat fluxes have a similar order of magnitude, and during the wet season the latent heat flux is the largest. The eddy covariance system had acceptable reliability in measuring heat flux, with actual evapotranspiration results comparing well with those obtained by using the water balance method. The energy balance closure had good results for the study area, with mean values of 0.93 and 0.86 for the dry and wet growing seasons respectively.

The global welfare impact of China: Trade integration and technological change

This paper evaluates the global welfare impact of China's trade integration and technological change in a multi-country quantitative Ricardian-Heckscher-Ohlin model.We simulate two alternative growth scenarios: a "balanced" one in which China's productivity grows at the same rate in each sector, and an "unbalanced" one in whichChina's comparative disadvantage sectors catch up disproportionately faster to theworld productivity frontier. Contrary to a well-known conjecture (Samuelson 2004),the large majority of countries experience significantly larger welfare gains whenChina's productivity growth is biased towards its comparative disadvantage sectors.This finding is driven by the inherently multilateral nature of world trade.

1199-000 Soil Nutrient Mass Balance Study

Key Points: • Iowa’s exceptional agricultural productivity is dependent upon nutrient‐rich soils with high carbon and nitrogen stocks. • Soil carbon and nitrogen stocks in Iowa corn‐soybean rotations are at significant risk of long‐term decline. • Soil carbon and nitrogen stocks are a function of crop residue inputs. • Nutrient input levels that do not maximize crop yield and residue production are likely to reduce soil carbon and nitrogen stocks. • If soil carbon and nitrogen stocks decline, water quality improvements become more difficult. • Soil carbon and nitrogen balances are extremely difficult to measure, but positive balances are essential to the future of Iowa agriculture. Recommended Actions: • Accurate measurement of soil carbon and nitrogen balances is exceptionally difficult, but can be accomplished with sufficient investment and long‐term planning. • The ideal approach will include a combination of measurements from farms and experimental networks that manipulate nutrient inputs. • With proper planning and cooperation, Iowa State University and the Iowa Department of Agriculture and Land Stewardship can address the concerns raised in this report regarding the future of Iowa’s soil resource and agricultural productivity.