959 resultados para Marginal lakes
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Conventional wisdom suggests that environmental non-governmental organizations (ENGOs) play a major role in pushing states towards more ambitious environmental policies. However, demonstrating that this presumption is in fact true is rather difficult, because the same system structures of democracies that may create more opportunities for ENGO activities are also, on their own, conducive to better environmental policies. This leaves open the possibility that the additional (marginal) impact of ENGOs on policy making is smaller than presumed. In trying to disentangle these effects, this paper examines the influence of ENGOs contingent on key structural characteristics of democratic systems. We develop the argument that presidential systems with a plurality electoral rule per se tend to provide more environmental public goods, which induces a smaller marginal impact of ENGOs. Conversely, parliamentary systems with a proportional representation electoral rule are likely to provide fewer environmental public goods, which allows for a larger marginal impact of ENGOs. We find robust empirical support for these hypotheses in analyses that focus on the ratification behavior of 75 democracies vis-à-vis 250 international environmental agreements in 1973–2002.
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Using miniature thermistors with integrated data loggers, the decrease in summer lake surface water temperature (LSWT) with increasing altitude a.s.l. was investigated in 10 Swiss Alpine lakes located between 613 m a.s.l. and 2339 m a.s.l. The LSWTs exhibit essentially the same short-term structure as regional air temperature, but are about 3 to 5°C higher than the air temperature at the altitude of the lake. LSWTs decrease approximately linearly with increasing altitude at a rate slightly greater than the surface air temperature lapse rate. Diel variations in LSWT are large, implying that single water temperature measurements are un- likely to be representative of the mean. Local factors will affect LSWT more than they affect air temperature, possibly resulting in severe distortion of the empirical relationship between the two. Several implications for paleoclimate reconstruction studies result. (1) Paleolimnologically reconstructed LSWTs are likely to be higher than the air temperatures prevailing at the altitude of the lake. (2) Lakes used for paleoclimate reconstruction should be selected to minimize local effects on LSWT. (3) The calibration of organism-specific quantitative paleotemperature inference models should not be based on single water temperature measurements. (4) Consideration should be given to calibrating such models directly against air temperature rather than water temperature. (5) The primary climate effect on the aquatic biota of high-altitude lakes may be mediated by the timing of the ice cover.
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from the journals of the late J. Frederick Elton, F.R.G.S., H.B.M. Consul at Mozambique ; edited and compiled by H.B. Cotterill
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Fifteen iron oxide accumulations from the bottoms of two Finnish lakes ("lake ores") were found to contain as much as 50% Fe. Differential X-ray powder diffraction and selective dissolution by oxalate showed that the samples consisted of poorly crystallized goethite and ferrihydrite. The crust ores of one lake had higher ferrihydrite to goethite ratios than the nodular ores of the other lake. The higher ferrihydrite proportion was attributed to a higher rate of Fe2+ supply from the ground water and/or a higher rate of oxidation as a function of water depth and bottom-sediment permeability. Values of Al-for-Fe substitution of the goethites determined from unit-cell dimensions agreed with those obtained from chemical extraction if the unit-cell volume rather than the c dimension was used. In very small goethite crystals a slight expansion of the a unit-cell dimension is probaby compensated by a corresponding contraction of the c dimension, so that a contraction of the c dimension need not necessarily be caused by Al substitution. The goethites of the two lakes differed significantly in their Al-for-Fe substitutions and hence in their unit-cell sizes, OH-bending characteristics, dehydroxylation temperatures, dissolution kinetics, and Mössbauer parameters. The difference in Al substitution (0 vs. 7 mole %) is attributed to the Al-supplying power of the bottom sediments: the silty-clayey sediments in one lake appear to have supplied A1 during goethite formation, whereas the gravelly-sandy sediments in the other lake did not. The compositions of the goethites thus reflect their environments of formation.
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The Tibetan Plateau (TP), including its surrounding mountain ranges, represents the largest store of ice outside the polar regions. It hosts numerous lakes as well as the head waters of major Asian rivers, on which billions of people depend, and it is particularly sensitive to climate change. The moisture transport to the TP is controlled by the Indian and Pacific monsoon and the Westerlies. Understanding the evolution of the interaction of these circulation systems requires studies on climate archives in different spatial and temporal contexts. The objective of this study is to learn more about the interannual variability of precipitation patterns across the TP and how different hydrologic systems react to different climatic factors. Aragonite shells of the aquatic gastropod Radix, which is widely distributed in the region, may represent suitable archives for inferring hydrologic and climatic signals in particularly high resolution. Therefore, sclerochronological studies of d18O and d13C ratios in Radix shells from seven lakes were conducted, each representing a different hydrologic and climatic setting, on a transect from the Pamirs across the TP. The shell patterns exhibit an increasing influence of precipitation and a decreasing influence of evaporation on the isotope compositions from west to east. d18O values of shells from lakes on the eastern and central TP (Donggi Cona, Yamdrok Yumco, Tarab Co) mirror monsoon signals, indicated by more negative values and higher variabilities compared to the more western lakes (Karakul, Bangong/Nyak, Manasarovar). In Yadang Co, located on the central southern TP, the monsoon rains did not reach the lake in the sampling year, although it is located in a region which is usually affected by monsoon circulation. The d18O values are used to differentiate the annual hydrological cycle into ice cover period, melt water period, precipitation period and evaporation period. d13C compositions in the shells particularly depend on specific habitats, which vary in biological productivity and in carbon sources. d18O and d13C patterns show a positive covariance in shells originating from large closed basins. The results show that Radix shells mirror general climatic differences between the seven lake regions. These differences reflect both regional and local climate signals in sub-seasonal resolution, without noticeable dependence on the particular lake system.
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Concentrations of major ions, silicate and nutrients (total N and P) were measured in samples of surface water from 28 lakes in ice-free areas of northern Victoria Land (East Antarctica). Sixteen lakes were sampled during austral summers 2001/02, 2003/04, 2004/05 and 2005/06 to assess temporal variation in water chemistry. Although samples showed a wide range in ion concentrations, their composition mainly reflected that of seawater. In general, as the distance from the sea increased, the input of elements from the marine environment (through aerosols and seabirds) decreased and there was an increase in nitrate and sulfate concentrations. Antarctic lakes lack outflows and during the austral summer the melting and/or ablation of ice cover, water evaporation and leaching processes in dry soils determine a progressive increase in water ion concentrations. During the five-year monitoring survey, no statistically significant variation in the water chemistry were detected, except for a slight (hardly significant) increase in TN concentrations. However, Canonical Correspondence Analysis (CCA) indicated that other factors besides distance from the sea, the presence of nesting seabirds, the sampling time and percentage of ice cover affect the composition of water in Antarctic cold desert environments.
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It is the purpose of this paper to record information concerning the distribution and occurrence of manganiferous concretions and other manganese oxide deposits that develop on certain lake bottoms. During the summer of 1935 several days were devoted to a study of this type of lake bottom deposit in various parts of Nova Scotia. Lake studies in Ontario have extended the known distribution from lakes on or near the Atlantic coast to lakes in southern Ontario. During the writer's first work on lacustrine manganiferous deposits the concretions of manganese oxide which were found were almost entirely limited to the relatively shallow parts of the lakes examined. Other lakes are now known where the manganese oxide appears to occur only in the maximum depths.
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El espacio público, atravesado por lugares de tránsito e interacción comunes de los individuos, constituye un terreno fundamental de la comunicación de todas las épocas. Este espacio mantiene a través de la historia del hombre significante su fuerza instrumental como espacio de difusión de significaciones. Éstas se producen ubicando mensajes, señales, símbolos en un segmento visual apropiado y de acceso público. En la construcción de este espacio visual público de comunicación intervienen sujetos comunicativos - locutores- que interpelan a las sociedades colaborando en la conformación de sus identidades y reproducen o trastocan sus representaciones, sus creencias, sus valores, sus conocimientos. Los mensajes son heterogéneos en sus formas, intenciones y lenguajes. El conjunto de estas marcas en el espacio varía, apareciendo y desapareciendo, reemplazándose, tomando nuevas formas y actualizándose necesariamente con el tiempo. Es un espacio continuamente mutante en sus formas y contenidos. Para el analista cultural representan una valiosa fuente de información para el acercamiento a la comprensión de la(s) identidad(es) de una sociedad. Cada texto existente en un momento y lugar determinado funciona entonces como un mensaje para los intervinientes en el proceso comunicativo del signo y además como una marca cultural de la época en la que se produce.
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Aproximar la narración del cuento "O ônibus branco" a aquellas sobre el mito de la barca del inferno es observar rastros de lo hegemónico en la escritura marginal, dirigirse hacia un tipo de información que se encuentra relacionada con las construcciones simbólicas de una cultura de instrucción y lecturas eruditas. ¿De qué lugares toma referencias la escritura producida más allá de los márgenes de la ciudad formal? Tal cuestionamiento impone una investigación que incide sobre la idea de que ciertas narrativas populares encuentran eco en lecturas más allá de aquellas disponibles en los medios masivos y acogen un repertorio culto
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Durante la temprana modernidad parte de los pobres fueron marginados y criminalizados debido a que no se insertaban en el mercado laboral, motivo que condujo a que fueran instigados al trabajo compulsivamente. La falta de especialización de estos hombres, así como su carácter urbano, fueron factores que contribuyeron a su inserción en diversas ocupaciones de servicio. Los criados no eran económicamente productivos, sino que su función tenía sentido en el marco socio-cultural, ya que servían a la reproducción de status de sus amos. Este tipo de actividades fueron ampliamente descriptas en el corpus de novelas que compone el género de la picaresca española, en el cual podemos observar un retrato sobre cómo imaginaron los literatos -que refractaron en sus obras una concepción social- las prácticas de los servidores. El Guzmán de Alfarache ilustra, a través de las sucesivas ocupaciones de servicio en que se emplea el protagonista, las formas de socialización que existían entre los mozos en el espacio doméstico, donde reproducían las conductas marginales en el marco de socialización "no marginal" que les era impuesto. El análisis que proponemos pretende indagar acerca de este problema en la crítica ilustración realizada por Mateo Alemán en El Guzmán...