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Dans ce document, nous évaluons l’impact de la microfinance sur des entrepreneurs panaméens, aussi bien sur leur niveau de performance de leurs entreprises que sur leur niveau de vie. Nous allons utiliser une méthode de différence-en-différence et un appariement pour voir l’effet des institutions financières sur les entrepreneurs. La principale contribution de ce mémoire est d’évaluer l’impact des prêts sur les entrepreneurs à travers le temps et pour ce, nous utilisons la différence-en-différence dynamique. D’après nos résultats, la microfinance ne semble pas avoir une influence significative sur les entrepreneurs avec la différence-en-différence. Ce constat est valable aussi bien sur les variables de performances des entrepreneurs que sur les variables de bien-être. Cependant, l’obtention de prêt auprès d’une IMF a un effet sur le revenu avec le modèle d’appariement.

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The abundance and distribution of biogenic, terrigenous and volcanic particles in the Panama Basin are markedly dependent on bottom topography and dissolution of calcite in the deeper parts of the basin. Of the coarse fraction (>62μ), foraminiferal tests and acidic volcanic glass shards are concentrated on the Cocos and Carnegie Ridges as lag deposits. Foraminiferal fragments are found on these ridge flanks and on the Malpelo Ridge due to reworking by bottom currents accentuated by dissolution of calcite with increasing depth. The finest calcite, probably coccoliths with fine foraminiferal fragments, together with the hydrodynamically light radiolarian skeletons are concentrated by bottom currents in the basin adjacent to the ridges. The foraminiferal calcite compensation depth in the basin is 3400 m. This relatively shallow depth probably reflects the high surface water productivity over the basin, although the pattern of productivity is not reflected in the pattern of biogenic sediments. Acidic volcanic glass appears to have been carried into the basin from Costa Rica, Colombia and Ecuador by easterly winds at altitudes of 1500 to 6000 m. Basaltic shards from the Galapagos Islands have been dispersed only over short distances to the west. Terrigenous sand-sized material is found on the edge of the continental shelf, where associated glauconite points to a relict origin, and along the northern Cocos Ridge, where contour currents may act as the dispersal mechanism. / Graduation date: 1973

In order to quantitatively examine the crustal structure of the Panama Basin without the benefit of local seismic refraction data, the following assumptions were made: (1) No significant lateral changes in density take place below a depth of 50 km. (2) The densities of the crustal layers are those of a 50-km standard section derived by averaging the results of 11 seismic refraction stations located in normal oceanic crust 10 to 40 million years (m. y. ) in age. (3) The density of the upper mantle is constant to a depth of SO km. (4) The thickness of the oceanic layer is normal in that region of the basin undergoing active spreading, exclusive of aseismic ridges. (5) The thickness of the transition layer is 1. 1 kin everywhere in the basin. Subject to these assumptions, the following conclusions are drawn from the available gravity, bathymetry, and sediment-thickness data: (1) Structurally, the aseismic ridges are surprisingly similar, characterized by a blocky, horst-like profile, an average depth of less than 2 km, an average depth to the Mohorovicic discontinuity of 17 km, and an average free-air anomaly of greater than +20 mgal. The fact that their associated free-air anomalies increase from near zero at their seaward ends to greater than +40 mgal at their landward ends suggests that the Cocos and Carnegie ridges are uplifted at their landward ends by lithospheric bending. (2) The centers of sea-floor spreading and fracture zones are characterized by a shoaling of the bottom and an apparent deepening of the Mohorovicic discontinuity. The only exception to this generalization is the northern end of the Panama fracture zone between the Cocos and Coiba ridges. (3) The Panama fracture zone and the fracture zone at 85°20'W longitude divide the Panama Basin into three provinces of different crustal thickness. Between these two fracture zones the crustal thickness is normal; west of 85°20W longitude it is greater than normal; and east of the Panama fracture zone it is less than normal. (4) In that part of the Panama Basin east of the Panama fracture zone there is a major discontinuity at 3°N latitude between a smooth, isostatically compensated crust to the south and an extremely rugged, uplifted crust to the north. An explanation for this discontinuity is the effect of the inflection in the shape of the continental margin at 3°N latitude on the eastward subductiori of the Nazca plate. / Graduation date: 1974

Holocene bulk sediment and component accumulation rates were measured in twenty-eight piston and gravity cores taken from the floor of the western Panama Basin and on the surrounding ridges. Radiocarbon ages and oxygen isotope curves provided Holocene age control in nine cores. Time datums in nineteen other cores were inferred by correlation of calcium carbonate curves to the dated cores. Dry bulk densities were measured in ten cores and were estimated in the others by an empirical relationship between dry bulk density and the percentages of sand, clay, and calcium carbonate. Other studies of the textural, mineralogical and sand fraction composition of near surface sediments in these cores provided analyses which could be used to obtain accumulation rates for these components. A general similarity between the map pattern of surface productivity and the patterns of carbonate and opal accumulation rates suggests a first order control of biogenic sedimentation by fertility of surface waters. Accumulation rates of terrigenous components are highest near the continents; the map and depth patterns suggest dispersal by currents shallower than 2000 m or by winds. It is inferred from textural component accumulation rate patterns that no significant regional redistribution of sediment by winnowing occurred during the Holocene. Deposition from deep thermohaline circulation probably increased the accumulation rates of silt, clay, and opaline components in the gaps between the western and eastern troughs. Calcium carbonate accumulation rates at equal depths are generally lower within 250 km of the edge of the continental shelf. Below 2000 m in high productivity regions > 250 km from the shelf calcium carbonate accumulation rates decrease linearly with depth according to a gradient of -3.3 gm CaCO₃/cm²/1000 yrs/ km. From this gradient, two independent estimates of the lysocline in this region, and a model of calcium carbonate accumulation, the average Holocene rate of supply of calcite from the surface is calculated to be 5-10 gm/cm²/1000 yrs. / Graduation date: 1976

Gravity and magnetic data from cruises by the R/V Yaquina in 1973 and the R/V Wecoma in 1975 provide new data that make possible the construction of a map of the free-air gravity anomalies at sea and simple Bouguer anomalies on lano in Panama, western Colombia, and the eastern Panama Basin. The gravity measurements and a wide angle reflection line provide data to construct a crustal and subcrustal cross section that starts at 6°N latitude, 80°22.7'W longitude in the Panama Basin and extends 800 km along a line which strikes N19°E across the Gulf of Panama and the Isthmus of Panama to the Colombia Basin. Two important features in the gravity map are the -90 and -100 mgal lows, oriented approximately east-west at 7°N and at 1O°N 1atitude. It is postulated that the southern low reflects a downwarp of the oceanic crust and the northern low reflects a shallow subductjon zone. Filtered magnetic anomalies and seismic refraction measurements support the conclusion that a piece of the oceanic crust which originated at the Nazca-Cocos Rift, forms the upper part of the continental shelf in the Gulf of Panama. The northernmost magnetic anomaly, approximately 50 km south of Panama City, is identified as anomaly number 9 in the geomagnetic scale and indicates 30 million years in age for these rocks which form part of the continental shelf of Panama. The model crustal cross section indicates a maximum thickness for the crust of 25 km for the Isthmus of Panama and a thickness of 17 km for the crust of the Gulf of Panama. The data and the model suggest that both a collision and subduction mechanism may be necessary to explain the tectonics and geology of the area. / Graduation date: 1979

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 374-386). Available also in a digital version from Dissertation Abstracts.

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This thesis explores the controversial Panama Canal expansion proposals using an analytical framework developed by Herman Daly, an ecological economist at the University of Maryland and a critic of traditional models economic development. At a time when nearly every nation seeks to increase the size of its economy, Daly has been an ardent advocate of setting limits to economic growth, arguing that, as the earth is materially closed, there cannot be infinite growth of the consumption of material and energy resources within a finite (nongrowing) biosphere. These limits should be defined by the regenerative and waste absorptive capacities of the biosphere. My objective here is to test the feasibility of implementing a policy at the local resource management level that is guided by the recognition of ecological limits to economic growth. I employ a water management technique developed by The Nature Conservancy called the Range of Variability Approach (RVA) and test its utility in setting an ecologically-based limit to water withdrawal and river system modification in the Panama Canal watershed. (Abstract shortened by UMI.)