An institution for the environment     

Vera Rich 《Marine pollution bulletin》1974,5(1):3-4

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The Belgian sandy beach ecosystem: a review     

Jeroen Speybroeck  Dries Bonte  Wouter Courtens  Tom Gheskiere  Patrick Grootaert  Jean-Pierre Maelfait  Sam Provoost  Koen Sabbe  Eric W. M. Stienen  Vera Van Lancker  Wouter Van Landuyt  Magda Vincx  & Steven Degraer 《Marine Ecology》2008,29(S1):171-185

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A protocol for classifying ecologically relevant marine zones,a statistical approach     

Els Verfaillie  Steven Degraer  Kristien Schelfaut  Wouter Willems  Vera Van Lancker 《Estuarine, Coastal and Shelf Science》2009

Mapping ecologically relevant zones in the marine environment has become increasingly important. Biological data are however often scarce and alternatives are being sought in optimal classifications of abiotic variables. The concept of ‘marine landscapes’ is based on a hierarchical classification of geological, hydrographic and other physical data. This approach is however subject to many assumptions and subjective decisions.  相似文献   

An overview of socio-economic and ecological perspectives of Fiji's inshore reef fisheries     

Lydia C.L. Teh  Louise S.L. Teh  Ben Starkhouse  U. Rashid Sumaila 《Marine Policy》2009,33(5):807-817

This paper reviews the socio-economic and ecological context of Fijian reef fisheries. This review is deemed necessary because improved understanding of the state and trends of Fiji's coral reef fisheries on a national level is required for designing an effective management plan for Fiji's inshore reef fisheries. The most important point that emerges from our review is that despite numerous studies of Fiji's reef fisheries, the current status of reef-associated fisheries at the national level is still uncertain due, mainly, to the lack of dependable data on the subsistence fisheries. This in turn leads to uncertainty about how the continuation of fishing, in particular, fishing focused on target species for the coral reef resources trade, will affect fishing communities and the ecosystem.  相似文献   

An analysis of Apollo lunar soil samples 12070,889, 12030,187, and 12070,891: Basaltic diversity at the Apollo 12 landing site and implications for classification of small‐sized lunar samples          下载免费PDF全文

Louise Alexander  Joshua F. Snape  Katherine H. Joy  Hilary Downes  Ian A. Crawford 《Meteoritics & planetary science》2016,51(9):1654-1677

Lunar mare basalts provide insights into the compositional diversity of the Moon's interior. Basalt fragments from the lunar regolith can potentially sample lava flows from regions of the Moon not previously visited, thus, increasing our understanding of lunar geological evolution. As part of a study of basaltic diversity at the Apollo 12 landing site, detailed petrological and geochemical data are provided here for 13 basaltic chips. In addition to bulk chemistry, we have analyzed the major, minor, and trace element chemistry of mineral phases which highlight differences between basalt groups. Where samples contain olivine, the equilibrium parent melt magnesium number (Mg#; atomic Mg/[Mg + Fe]) can be calculated to estimate parent melt composition. Ilmenite and plagioclase chemistry can also determine differences between basalt groups. We conclude that samples of approximately 1–2 mm in size can be categorized provided that appropriate mineral phases (olivine, plagioclase, and ilmenite) are present. Where samples are fine‐grained (grain size <0.3 mm), a “paired samples t‐test” can provide a statistical comparison between a particular sample and known lunar basalts. Of the fragments analyzed here, three are found to belong to each of the previously identified olivine and ilmenite basalt suites, four to the pigeonite basalt suite, one is an olivine cumulate, and two could not be categorized because of their coarse grain sizes and lack of appropriate mineral phases. Our approach introduces methods that can be used to investigate small sample sizes (i.e., fines) from future sample return missions to investigate lava flow diversity and petrological significance.  相似文献   

Summer precipitation variability over South America on long and short intraseasonal timescales     

Paula L. M. Gonzalez  Carolina S. Vera 《Climate Dynamics》2014,43(7-8):1993-2007

A dipole pattern in convection between the South Atlantic convergence zone and the subtropical plains of southeastern South America characterizes summer intraseasonal variability over the region. The dipole pattern presents two main bands of temporal variability, with periods between 10 and 30 days, and 30 and 90 days; each influenced by different large-scale dynamical forcings. The dipole activity on the 30–90-day band is related to an eastward traveling wavenumber-1 structure in both OLR and circulation anomalies in the tropics, similar to that associated with the Madden–Julian oscillation. The dipole is also related to a teleconnection pattern extended along the South Pacific between Australia and South America. Conversely, the dipole activity on the 10–30-day band does not seem to be associated with tropical convection anomalies. The corresponding circulation anomalies exhibit, in the extratropics, the structure of Rossby-like wave trains, although their sources are not completely clear.  相似文献   

The freshwater lens of Benjamín Aceval,Chaco, Paraguay: a terrestrial analogue of an oceanic island lens     

Georg Houben  Ursula Noell  Sara Vassolo  Christoph Grissemann  Mebus Geyh  Susanne Stadler  Eduardo J. Dose  Sofia Vera 《Hydrogeology Journal》2014,22(8):1935-1952

The occurrence of a freshwater lens in the Paraguayan Chaco, 900 km away from the ocean, is reported. It is located underneath sandstone hills, surrounded by lowlands with predominantly saline groundwater. Its geometry was delineated using geoelectrical and electromagnetic investigations. The unusual height of the fresh groundwater level can be attributed to the presence of a confining layer at depth. The lens receives its recharge exclusively from rainfall during the hot and humid summer months. It predominantly contains water predating the atmospheric atomic bomb tests, some of it probably up to a thousand or more years old. The water balance shows that extraction currently does not exceed recharge in normal years. However, the available volume of groundwater leaves little room for a further increase of extraction in the future. Recharge is augmented by return flow from thousands of latrines and cess pits, and this has lead to widespread contamination of the groundwater by faecal bacteria.  相似文献   

Structural evolution of the Orange Basin gravity-driven system,offshore Namibia     

Jose de Vera  Pablo GranadoKen McClay 《Marine and Petroleum Geology》2010

The Orange Basin records the development of the Late Jurassic to present day volcanic-rifted passive margin of Namibia. Regional extension is recorded by a Late Jurassic to Lower Cretaceous Syn-rift Megasequence, which is separated from a Cretaceous to present day post-rift Megasequence by the Late Hauterivian (ca. 130 Ma) break-up unconformity. The Late Cretaceous Post-rift evolution of the basin is characterized by episodic gravitational collapse of the margin. Gravitational collapse is recorded as a series of shale-detached gravity slide systems, consisting of an up-dip extensional domain that is linked to a down-dip zone of contraction domain along a thin basal detachment of Turonian age. The extensional domain is characterized by basinward-dipping listric faults that sole into the basal detachment. The contractional domain consists of landward-dipping listric faults and strongly asymmetric basinward-verging thrust-related folds. Growth stratal patterns suggest that the gravitational collapse of the margin was short-lived, spanning from the Coniacian (ca. 90 Ma) to the Santonian (ca. 83 Ma). Structural restorations of the main gravity-driven system show a lack of balance between up-dip extension (24 km) and down-dip shortening (16 km). Gravity sliding in the Namibian margin is interpreted to have occurred as a series of episodic short-lived gravity sliding between the Cenomanian (ca. 100 Ma) and the Campanian (ca. 80 Ma). Gravity sliding and spreading are interpreted to be the result of episodic cratonic uplift combined with differential thermal subsidence. Sliding may have also been favoured by the presence of an efficient detachment layer in Turonian source rocks.  相似文献   

Shallow structures at the outer Calabrian accretionary wedge (NW Ionian Sea): new insights from recently migrated reflection data     

Vera Valenti 《地学学报》2010,22(6):453-462

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Observations of photometric profiles of two planetary nebulae     

R. Louise  A. Kherous 《Astrophysics and Space Science》1991,176(1):149-162

It is noted that the Abel integral of a Gaussian function is a Gaussian function. This special property is used in order to develop an analytic method for studying photometric profile in Planetary Nebulae. Monochromatic observations have been made at the Haute-Provence Observatory using the RCA-CCD (320×512 pixels) mounted at theF/6 Newtonian focus of the 1.2 m telescope. Among the observed nebulae, two of them (NGC 6778 and NGC 7354) are regular enough to test the photometric profile method. The nebular emissivity per volume unit is then obtained for H⁺ and O⁺⁺ ions.  相似文献