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631.
632.
Jos I Saiz Nuria Anadn Javier Cristobo Oscar Garca-Alvarez Gerardo Garca-Castrillo Eduardo Lpez Cruz Palacn Jess S Troncoso Ana Ramos 《海洋学报(英文版)》2013,32(6):47-55
Insular marine biotas are often richer in faunal diversity than those from the open sea in the same geographical region. The existence of particular island effects were tested under polar conditions by comparing infaunal benthic assemblages on Peter I Island with those of similar latitudes in the open ocean at the Bellingshausen Sea and also from the coast of the Antarctic Peninsula. Sampling was carried out aboard the R/V Hespérides during the expedition named BENTART-2003 from 24 January to 3 March 2003. Benthic samples were collected at 18 stations ranging from 90 to 2 044 m depth, using an USNEL-type box corer (BC) dredge. Representatives of 32 higher taxa of invertebrates were found. Univariate and multivariate analyses revealed various patterns in the data. First, significant differences in polychaete abundance were detected between the stations located in the open sea and the remaining sites (island plus mainland sites). Bivalve abundances were also distinct between island and mainland sampling sites. Sediment columns taken from the island seafloor exhibited the highest rate of bioturbation by the infauna. These findings confirm the model that islands develop distinct assemblages characterized by the enhancement of the benthic communities even in cold waters. Several abiotic factors were measured simultaneously at the seafloor and along the water column to investigate faunal distribution patterns. Significant correlations were found between the benthic assemblages and a combination of two environmental variables: "island effect" (measured as a categorical variable) and the redox state of sediments. Richer and more complex benthic assemblages were found in Peter I Island’s sea bottom, whereas the more depauperate bottoms remained in the open sea. 相似文献
633.
Gustavo M. Martins Rita F. Patarra Nuno V. Álvaro Afonso C. L. Prestes Ana I. Neto 《Marine Ecology》2013,34(3):289-297
A better understanding of biological systems can only be gained if we understand what processes are important and how they operate to determine the distribution of organisms. Coastal orientation and depth can influence environmental conditions, including the degree of water motion and availability of light, which in turn may influence the horizontal and vertical patterns of organism distribution. Here, we used a mixed‐model design to examine the effects of coastal orientation and depth on the structure of benthic assemblages by comparing the abundance and distribution of macroalgae and invertebrates in shallow and deep waters on the opposing coasts of São Miguel. Generally, coastal orientation had little influence on the distribution of most taxa. In contrast, significant differences were generally associated with depth, although patterns were spatially variable at the scale of locations. This study suggests that depth, and processes operating at the scale of location, but not at the scale of the coast, have an important influence on these assemblages, and that failure to recognise such a scale of variability may hamper our ability to better understand the processes that structure these communities. 相似文献
634.
Boris Shustov Mikhail Sachkov Ana I. Gómez?de?Castro Klaus Werner Norbert Kappelmann Alexander Moisheev 《Astrophysics and Space Science》2011,335(1):273-282
Continuous access to the UV domain has been considered of importance to astrophysicists and planetary scientists since the
mid-sixties. However, the future of UV missions for the post-HST era is believed by a significant part of astronomical community
to be less encouraging. We argue that key science problems of the coming years will require further development of UV observational
technologies. Among these hot astrophysical issues are: the search for missing baryons, revealing the nature of astronomical
engines, properties of atmospheres of exoplanets as well as of the planets of the Solar System etc. We give a brief review
of UV-missions both in the past and in the future. We conclude that UV astronomy has a great future but the epoch of very
large and efficient space UV facilities seems to be a prospect for the next decades. As to the current state of the UV instrumentation
we think that this decade will be dominated by the HST and coming World Space Observatory-Ultraviolet (WSO-UV) with a 1.7 m
UV-telescope onboard. The international WSO-UV mission is briefly described. It will allow high resolution/high sensitivity
imaging and high/low resolution spectroscopy from the middle of the decade. 相似文献
635.
636.
Laurent Koechlin Denis Serre Paul Deba Roser Pelló Christelle Peillon Paul Duchon Ana Ines Gomez de Castro Margarita Karovska Jean-Michel Désert David Ehrenreich Guillaume Hebrard Alain Lecavelier des Etangs Roger Ferlet David Sing Alfred Vidal-Madjar 《Experimental Astronomy》2009,23(1):379-402
The Fresnel Interferometric Imager has been proposed to the European Space Agency (ESA) Cosmic Vision plan as a class L mission.
This mission addresses several themes of the CV Plan: Exoplanet study, Matter in extreme conditions, and The Universe taking shape. This paper is an abridged version of the original ESA proposal. We have removed most of the technical and financial issues,
to concentrate on the instrumental design and astrophysical missions. The instrument proposed is an ultra-lightweight telescope,
featuring a novel optical concept based on diffraction focussing. It yields high dynamic range images, while releasing constraints
on positioning and manufacturing of the main optical elements. This concept should open the way to very large apertures in
space. In this two spacecraft formation-flying instrument, one spacecraft holds the focussing element: the Fresnel interferometric
array; the other spacecraft holds the field optics, focal instrumentation, and detectors. The Fresnel array proposed here
is a 3.6 ×3.6 m square opaque foil punched with 105 to 106 void “subapertures”. Focusing is achieved with no other optical element: the shape and positioning of the subapertures (holes
in the foil) is responsible for beam combining by diffraction, and 5% to 10% of the total incident light ends up into a sharp
focus. The consequence of this high number of subapertures is high dynamic range images. In addition, as it uses only a combination
of vacuum and opaque material, this focussing method is potentially efficient over a very broad wavelength domain. The focal
length of such diffractive focussing devices is wavelength dependent. However, this can be corrected. We have tested optically
the efficiency of the chromatism correction on artificial sources (500 < λ < 750 nm): the images are diffraction limited, and the dynamic range measured on an artificial double source reaches 6.2
10 − 6. We have also validated numerical simulation algorithms for larger Fresnel interferometric arrays. These simulations yield
a dynamic range (rejection factor) close to 10 − 8 for arrays such as the 3.6 m one we propose. A dynamic range of 10 − 8 allows detection of objects at contrasts as high as than 10 − 9 in most of the field. The astrophysical applications cover many objects in the IR, visible an UV domains. Examples are presented,
taking advantage of the high angular resolution and dynamic range capabilities of this concept. 相似文献
637.
Ana I. Dittel C.E. Epifanio Juan Bautista Chavarria 《Estuarine, Coastal and Shelf Science》1985,20(5):593-602
Tropical blue crabs Callinectes arcuatus were collected by trawling in the Gulf of Nicoya on the Pacific coast of Costa Rica, Central America. The gulf population was generally dominated by females. Adult females were common in the upper, more estuarine regions of the gulf during rainy season, but appeared to migrate to the lower gulf during dry season for spawning. Biomass varied with seasonal changes in abundance, but was generally similar to biomass of C. sapidus in Chesapeake Bay. Analysis of size frequency indicated that the population is numerically dominated by adults during January and February and that juveniles are common during the remainder of the year. Extrapolation of available data suggests that female crabs reach maturity in approximately one year after hatching. 相似文献
638.
Helio S. Migon Ana Beatriz S. Monteiro 《Stochastic Environmental Research and Risk Assessment (SERRA)》1997,11(2):115-127
The rainfall-runoff modeling is very useful for forecasting purposes. A good methodology for forecasting the future stream
flow is a key requirement for designers and operators of water resources systems.
A compromise between conceptual and classical time series modeling is applied to model the relationship between rainfall and
runoff. The dynamic nonlinear model is composed of a probability distribution describing the observation, a link function
relating its mean to the so called state parameters and a system of equations defining the evolution of these parameters.
Its Bayesian nature permits to take into account subjective information, making forward intervention, defining monitoring
schemes and introducing smoothing facilities.
An application using the data of Fartura river's basin is reported. The assessment of the prior distribution is discussed
and the predictive performance of the linear and the non-linear models is reported. 相似文献
639.
Julio Cesar Wasserman Ana Maria G Figueiredo Fabio Pellegatti Emmanoel V Silva-Filho 《Journal of Geochemical Exploration》2001,72(2):1013
The geochemistry of Sepetiba Bay was studied in four sediment cores using a multi-element approach. Two cores were sampled in the more contaminated eastern part of the bay and two cores were sampled in the western region. The aim was to determine whether less common elements like the rare earths or the actinides are associated with contaminant metals like zinc in the Bay. Samples were analysed by instrumental neutron activation analysis that permits the quantification of total concentrations of metals (Ba, Co, Cr, Cs, Fe, Hf, Rb, Sc, Zn), rare earth elements (Ce, Eu, La, Lu, Sm and Yb), actinides (Th, U), non-metals and semi-metals (As, Br). Organic carbon and total sulphur were also analysed. The results show very strong zinc contamination in the top layers (more than 1000 μg g−1) and background concentrations in the bottom (15 μg g−1). Elements like chromium which would be expected to be released by the heavy industries of Sepetiba Bay, did not show a contamination profile, and concentrations remained close to those of natural environments. No evidence of any association between the zinc and other potential contaminant elements could be identified in this work. 相似文献