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151.
152.
This paper presents an investigation based on the testimonies of ethnic Bamar or Burman women migrant workers in the ethnically diverse 'borderland' town of Tachilek, Myanmar and interviews with their relatives in the home village in the central Burman heartlands. We examine how the concept of relational places, here involving a village in the central Mandalay Division and a town in the Myanmar–Thailand borderland, is related to differential power relations affecting the women migrants. We focus on the ways that gender identity and social position are limited by the relational places of community elders and the migrant women themselves, and suggest that the relational places of migrants in Myanmar are constructed through the nexus of varied forms of state control in both the central Burman heartlands and the multiethnic borderlands of the country. 相似文献
153.
Carlos M. Duarte Núria Marbà Dorte Krause-Jensen María Sánchez-Camacho 《Estuaries and Coasts》2007,30(4):652-656
The power of equations predicting seagrass depth limit (Zc) from light extinction (K
z) was tested on data on seagrass depth limits collected from the literature. The test data set comprised 424 reports of seagrass
colonization depth and water transparency, including data for 10 seagrass species. This data set confirmed the strong negative
relationship betweenZ
c andK
z. The regression equation in Duarte (1991) overestimated the realized seagrass colonization depths at colonization depths
< 5 m, while there was no prediction bias above this threshold. These results indicated that seagrass colonizing turbid waters
(K
z 0.27 m-1) have higher apparent light requirements than those growing in clearer waters. The relationship between seagrass colonization
depth and light attenuation shifts at a threshold of light attenuation of 0.27 m-1, requiring separate equations to predictZ
c for seagrass growing in more turbid waters and clearer waters, and to set targets for seagrass restoration and conservation
efforts. 相似文献
154.
The paper analyses the causes of flood occurrence in the Gran La Plata, Buenos Aires Province, Argentina, and the changes
that have occurred since the 1970s. The area is characterized by serious deficiencies in the use and management of water resources.
The main factors are: (1) flood risk information is not updated; (2) urban building organization does not consider the flood
risk; (3) the topography and other physical features are not taken into account in urban development. This research considers
some specific problems, especially in data availability, and suggests ways to solve them, including improved analytical methodology.
One of the main objectives is to analyse flood risk in social terms, producing a map of flood risk from the “human social
vulnerability” point of view. The results suggest that flood risk has increased since the 1980s and that this is associated
with changes in precipitation patterns that have also been aggravated by lack of controls on urban development. The poorer
areas with the lowest level of infrastructure and public services, many of them developed over the last quarter-century, are
especially vulnerable. 相似文献
155.
Carlos Marín-Lechado Jesús Galindo-Zaldívar Luís Roberto Rodríguez-Fernández Antonio Pedrera 《Pure and Applied Geophysics》2007,164(1):1-21
The boundary between the Alboran Sea and Betic Cordillera is a good example of a fold related mountain front in the Internal
Zone of an alpine mountain range. Since the late Miocene, NNW-SSE convergence between the Eurasian and African plates has
produced shortening and related orthogonal extension. To improve the characterisation of the geometry of the deep structure
in the region and to establish the recent tectonic evolution of the mountain front, well logs and newly acquired geophysical
data (multichannel reflection seismic and gravimetric surveys) have been interpreted and integrated with available surface
data. The most marked tectonic structure corresponds to large antiforms and synforms of ENE-WSW trend which are related to
mountain ranges and basins, respectively. The fold belt continues toward the northern continental shelf of the Alboran Sea.
The fold vergence is generally northwards and its amplitude decreases progressively towards SSE, until disappearring in a
sharp boundary where the reflectors are undeformed. The deep geometry suggests that fold growth started during upper Tortonian
times and continued its activity up to Pliocene or even Quaternary times. The NNW-SSE compression produces crustal thickening
and a regional and progressive southwards emersion. The location of main present-day deformation fronts in the Internal Zones
contrasts with classical models where the deformation progresses towards the frontal part of External Zones of cordilleras.
In addition, this fold-related deformation mountain front has features different from fault related fronts, as it does not
show a sharp boundary, and folds that determine rectilinear mountain boundaries decrease progressively in amplitude or in
wavelength up to undeformed areas. 相似文献
156.
This work was focused on the assessment of changes occurring in crop production and climate during the 20th century in Argentina.
The study was carried out for nine sites located in the Pampas region that are representative of contrasting environments.
We have considered the four main crops cultivated in this area (wheat, maize, sunflower and soybean). Historical climatic
data and crop production related variables (yield, planted area, harvested area) were analyzed and, by means of crop simulation
models, we quantified the impact of climate on crop yields. Changes occurring in climate during the three last decades of
the 20th century were characterized by important increases in precipitation especially between October and March, decreases
in maximum temperature and solar radiation in particular during spring and summer and increases in minimum temperature during
almost all of the year. These changes contributed to increases in yields, especially in summer crops and in the semiarid zone,
mostly due to increases in precipitation, although changes in temperature and radiation also affected crop yields but to a
lesser extent. Comparing the period 1950–1970 with 1971–1999, yields increases attributable to changes in climate were 38%
in soybean, 18% in maize, 13% in wheat, and 12% in sunflower while mean observed yield increases were 110% for maize, 56%
for wheat and 102% for sunflower. 相似文献
157.
Joaquín Bohigas Mauricio Tapia María Teresa Ruiz † Miguel Roth 《Monthly notices of the Royal Astronomical Society》2000,312(2):295-300
Continuum-subtracted dereddened images in the light of several atomic lines show the presence of an extended bipolar nebula surrounding η Carinae with size ∼100×45 arcsec2 (1.3×0.5 pc2 ). This feature is best delineated in [O iii ] 5007. The geometrical disposition and mass of the shell suggest that it was formed by mass ejections from η Carinae. The dynamic age of the nebula is ∼13 000/ V 7 yr, where V 7 is the mean expansion velocity in 100 km s−1 , and its mass is between 5 and 10 M⊙ . The nebula is photoionized and composed of unprocessed material. The major axes of the nebula and of the Homunculus are nearly perpendicular. We also report the discovery of elongated emission knots prominent in [N ii ] located 64 to 100 arcsec away from η Carinae, which implies that they were ejected either centuries ago or at a more recent date but with extremely large velocities. 相似文献
158.
Tephrochronology is a powerful tool for dating sedimentary sequences, especially in Patagonia, where a large number of active volcanoes have produced frequent historical eruptions. Short lacustrine sedimentary sequences were extracted from the lakes Moreno Oeste and Ton?ek (Nahuel Huapi National Park). Seventeen volcanic ash layers were identified in both cores, 210Pb and 137Cs were used for dating techniques, and historical volcanic records were employed for correlation. White pumice and glass shards from the tephras were characterised by measuring major and trace element contents by instrumental neutron activation analysis. Two volcanic sources – the Cordón Caulle and the Calbuco volcanoes – were recognised as the prevailing systems that impacted the area in the past 800–1000 a. The Calbuco volcano was mainly responsible for the nine tephras identified in the Lake Ton?ek sequence. Four of these nine tephras also contained material from the Cordón Caulle complex, and could be interpreted as composite tephras or possible reworked ones. The Calbuco volcano showed predominant influences in the Lake Moreno Oeste sequence. Six of the eight tephras identified in such a sequence were from the Calbuco volcano, and three of these six contained material from the Cordón Caulle complex. The other two were from the Cordón Caulle complex, with contributions from the Calbuco volcano in one of them. These findings show that the high frequency of volcanic events in the study region demands an accurate characterisation of the products generated by each source, as well as an evaluation of their spatial distribution, to obtain a consistent framework for dating recent environmental changes. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
159.
Paulina Montero Giovanni Daneri Humberto E. González Jose Luis Iriarte Fabián J. Tapia Lorena Lizárraga Nicolas Sanchez Oscar Pizarro 《Continental Shelf Research》2011,31(3-4):202-215
We characterized the seasonal cycle of productivity in Reloncaví Fjord (41°30′S), Chilean Patagonia. Seasonal surveys that included measurements of gross primary production, community respiration, bacterioplankton secondary production, and sedimentation rates along the fjord were combined with continuous records of water-column temperature variability and wind forcing, as well as satellite-derived data on regional patterns of wind stress, sea surface temperatures, and surface chlorophyll concentrations. The hydrography and perhaps fjord productivity respond to the timing and intensity of wind forcing over a larger region. Seasonal changes in the direction and intensity of winds, along with a late-winter improvement in light conditions, may determine the timing of phytoplankton blooms and potentially modulate productivity cycles in the region.Depth-integrated gross primary production estimates were higher (0.4–3.8 g C m?2 d?1) in the productive season (October, February, and May), and lower (0.1–0.2 g C m?2 d?1) in the non-productive season (August). These seasonal changes were also reflected in community respiration and bacterioplankton production rates, which ranged, respectively, from 0.3 to 4.8 g C m?2 d?1 and 0.05 to 0.4 g C m?2 d?1 during the productive and non-productive seasons and from 0.05 to 0.6 g C m?2 d?1 and 0.05 to 0.2 g C m?2 d?1 during the same two periods. We found a strong, significant correlation between gross primary production and community respiration (Spearman, r=0.95; p<0.001; n=12), which suggests a high degree of coupling between the synthesis of organic matter and its usage by the planktonic community. Similarly, strong correlations were found between bacterioplankton secondary production and both gross primary production (Spearman, r=0.7, p<0.05, n=9) and community respiration (Spearman, r=0.8, p<0.05, n=9), indicating that bacterioplankton may be processing an important fraction (8–59%) of the organic matter produced by phytoplankton in Reloncaví Fjord. In winter, bacterial carbon utilization as a percentage of gross primary production was >100%, suggesting the use of allochthonous carbon sources by bacterioplankton when the levels of gross primary production are low. Low primary production rates were associated with a greater contribution of small cells to autotrophic biomass, highlighting the importance of small-sized plankton and bacteria for carbon cycling and fluxes during the less productive winter months. Fecal pellet sedimentation was minimal during this period, also suggesting that most of the locally produced organic carbon is recycled within the microbial loop. During the productive season, on the other hand, the area exhibited a great potential to export organic matter, be it to higher trophic levels or vertically towards the bottom. 相似文献
160.