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111.
The diversity of serphitid wasps (Proctotrupomorpha: Serphitoidea) in Early Cretaceous (Albian) amber from Spain is described. Four new species have been found representing the genera Serphites Brues 1937, Aposerphites Kozlov and Rasnitsyn 1979, and Microserphites Kozlov and Rasnitsyn 1979. From the Peñacerrada I (Moraza) outcrop two species are described as Aposerphites angustus Ortega-Blanco, Delclòs, Peñalver and Engel, new species and Serphites lamiak, new species. A single species was found at the San Just (Teruel) outcrop and is described as S. silban, new species. Another single specimen was found in El Soplao (Cantabria) outcrop, described as Microserphites soplaensis, new species. This last specimen is especially interesting in sharing typical serphitid and mymarommatoid characters, giving additional support to the apparent close relationship of both groups. 相似文献
112.
113.
In the plane, consider a compact set with nonempty interior and piecewise C
1 boundary such that any line segment crosses this boundary at only finitely many points. Then the second derivatives of the
geometric covariogram of the compact set at the origin are related to geometrical characteristics of the set boundary. Specifically,
the mean second derivative is zero when the boundary has no singular point, it is positive when the boundary has finitely
many vertices but no cusp, and it is infinite when the boundary has at least one cusp. 相似文献
114.
V. Tu Do Xavier de MontaudouinNicolas Lavesque Hugues BlanchetHervé Guyard 《Estuarine, Coastal and Shelf Science》2011
This study provided evidence that Zostera noltii presence affects macrofauna community structure independently from median sediment grain-size and that the notion of ecosystem health is rather subjective: in the present case, we recorded “good health” in terms of seagrass development, “no impact” in terms of macrobenthic biotic indices and “negative effect” for a given key-population. The occurrence and development of a Z. noltii seagrass bed was surveyed at Banc d’Arguin, Arcachon Bay (France), to estimate the modification of the macrozoobenthic community and of the dynamics of a key-population for the local ecosystem, – the cockle Cerastoderma edule. Even though median grain-size of the sediment decreased only at the very end of the survey, i.e. when seagrass totally invaded the area, most of the macrofauna community characteristics (such as abundance and biomass) increased as soon as Z. noltii patches appeared. The structure of the macrofauna community also immediately diverged between sand and seagrass habitats, without however modifying the tested biotic indices (BENTIX, BOPA, AMBI). The health of the cockle population (growth, abundance, recruitment) was impacted by seagrass development. Related parasite communities slowly diverged between habitats, with more parasites in the cockles from seagrass areas. However, the number of parasites per cockle was always insufficient to alter cockle fitness. 相似文献
115.
Xavier López-Medellín Alicia CastilloExequiel Ezcurra 《Ocean & Coastal Management》2011,54(4):318-329
Mangroves in Northwestern Mexico are vital to maintain coastal environments healthy, to provide nutrients for several food chains, and to supply valuable goods and services that sustain and improve human livelihoods. Many of these values offer a range of opportunities for economic development that attract workers, investors and developers. Recently, federal privatization policies have promoted an accelerated coastal development of this region to obtain large profits in short times, creating competing and overlapping interests to use coastal environments and control key resources. Such intense developments are modifying the ecological conditions of many coastal areas, threatening the provision of important ecosystem services to society. After years of centralized decisions, new paradigms are needed to achieve a coastal management that ensures long-term ecosystem maintenance, fair resource use and social equity. Recognizing the multiplicity of actors involved in coastal management and using a qualitative research methodology, we identified and explored the perspectives of different key stakeholders in the states of Baja California Sur and Sonora, Mexico, to better understand their views on mangroves use and management as well as the interaction among them. We discuss similarities and/or discrepancies found among stakeholders’ perceptions by describing their central ideas and identifying overlapping interests that may create conflicts when defining development and conservation programs or formulating policies. This information also intends to encourage further research on the social-ecological system of the coasts in Northwestern Mexico and to contribute to address coastal management issues in integrated ways that consider the social dimension through documenting stakeholders’ narratives in the future. 相似文献
116.
Xavier Hernandez † Andrea Ferrara 《Monthly notices of the Royal Astronomical Society》2001,324(2):484-490
We explore the predictions of the standard hierarchical clustering scenario of galaxy formation, regarding the numbers and metallicities of PopIII stars that are likely to be found within our Galaxy today. By PopIII we refer to stars formed at large redshift ( z >4), with low metallicities ([ Z /Z⊙ ]<−2.5) and in small systems (total mass ≲ 2×108 M⊙ ) that are extremely sensitive to stellar feedback, and which through a prescribed merging history end up becoming part of the Milky Way today. An analytic, extended Press–Schechter formalism is used to obtain the mass functions of haloes which will host PopIII stars at a given redshift, and which will end up in Milky Way sized systems today. Each of these is modelled as a mini-galaxy, with a detailed treatment of the dark halo structure, angular momentum distribution, final gas temperature and disc instabilities, all of which determine the fraction of the baryons that are subject to star formation. The use of new primordial metallicity stellar evolutionary models allows us to trace the history of the stars formed, and give accurate estimates of their expected numbers today and their location in L /L⊙ versus T /K Hertzsprung–Russell (HR) diagrams. A first comparison with observational data suggests that the initial mass function (IMF) of the first stars was increasingly high-mass weighted towards high redshifts, levelling off at z ≳9 at a characteristic stellar mass scale m s =10–15 M⊙ . 相似文献
117.
The Demeter microsatellite and ground segment 总被引:4,自引:0,他引:4
Thibery Cussac Marie-Anne Clair François Buisson Michel Ledu Christian Elisabelar Xavier Passot Nelly Rey 《Planetary and Space Science》2006,54(5):413-427
The Demeter program is the first application of the Myriade microsatellite program conducted by the Cnes (French Space Agency) since 1997. The Myriade objective was to benefit from the miniaturization of the technologies to develop a product with a reduced size, weight and cost able to implement either scientific missions, demonstrators or operational applications in different areas: earth observation, astronomy, fundamental physics or telecommunications, within limited financial budget.The Demeter satellite was launched in end of June 2004, from Baikonour, aboard a Dnepr launcher, on a sun synchronous orbit at 710 km altitude. Its main scientific objectives are the detection and characterization of ionosphere electrical and magnetic disturbances in connection with a seismic activity.The scientific payload has been built by French scientific institutes (LPCE, CESR, CETP) involved in external and internal geophysics and by SSD/ESTEC (ESA). It is composed of several electrical and magnetic sensors, an ion spectrometer, an energetic particle analyzer and a Langmuir probe.The Demeter platform is designed in order to offer a high level of performances in terms of power, attitude and orbit control, data storage and transmission, flexibility. For example the large amount of scientific data is transmitted to the ground station with a high data rate telemetry link in X band.This paper describes the Demeter satellite and ground segment. It focuses on the specific design adaptations of the Myriade product for Demeter and it presents the preliminary in orbit platform performances. 相似文献
118.
Jordi Portell Enrique García-Berro Xavier Luri Alberto G. Villafranca 《Experimental Astronomy》2006,21(3):125-149
Gaia is the most ambitious space astrometry mission currently envisaged and it will be a technological challenge in all its
aspects. Here we describe a proposal for the data compression system of Gaia, specifically designed for this mission but based
on concepts that can be applied to other missions and systems as well. Realistic simulations have been performed with our
Telemetry CODEC software, which performs a stream partitioning and pre-compression to the science data. In this way, standard
compressors such as bzip2 or szip boost their performance and decrease their processing requirements when applied to such pre-processed data. These simulations
have shown that a lossless compression factor of 3 can be achieved, whereas standard compression systems were unable to reach
a factor of 2.
相似文献
119.
India experienced a heavy rainfall event in the year 2013 over Uttarakhand and its adjoining areas, which was exceptional as it witnessed the fastest monsoon progression. This study aims to explore the causative factors of this heavy rainfall event leading to flood and landslides which claimed huge loss of lives and property. The catastrophic event occurred from 14th to 17th June, 2013 during which the state received 375% more rainfall than the highest rainfall recorded during a normal monsoon season. Using the high resolution precipitation data and complementary parameters, we found that the mid-latitude westerlies shifted southward from its normal position during the intense flooding event. The southward extension of subtropical jet (STJ) over the northern part of India was observed only during the event days and its intensity was found to be increasing from 14th to 16th June. The classical theory of westward tilt of mid-latitude trough with height, which acts to intensify the system through the transfer of potential energy of the mean flow, is evident from analysis of relative vorticity at multiple pressure levels. On analysing the North Atlantic Oscillation (NAO), negative values were observed during the event days. Thus, the decrease in pressure gradient resulted in decrease of the intensity of westerlies which caused the cold air to move southward. During the event, as the cold air moved south, it pushed the mid-latitude westerlies south of its normal position during summer monsoon and created a conducive atmosphere for the intensification of the system. 相似文献
120.
Xavier Le Pichon Caner İmren Claude Rangin A. M. Celâl Şengör Muzaffer Siyako 《International Journal of Earth Sciences》2014,103(1):219-231
We use about 800 km of multichannel exploration seismic reflection profiles of the seventies as well as the results of three drill holes that penetrated the sedimentary cover down to the Upper Cretaceous basement to describe a continuous gently curvilinear, south-concave zone of deformation about 10 km wide that extended over the whole southern shelf of the Sea of Marmara from the Gulf of Gemlik to the Dardanelles Straits in Lower Pliocene time, about 4 Ma. We call this zone of deformation the South Marmara Fault (SMF) system and propose that the SMF was then a branch of the dextral North Anatolian Fault. This branch passed to the north of the Marmara Island Eocene block and thus had a south-facing concavity. This curvature resulted in a significant component of shortening in the western part of the fault. The SMF was deactivated at the end of Lower Pliocene, about 3.5 Ma, except for its easternmost branch between the Gulf of Gemlik and ?mral? Island where about 5 mm/year of dextral motion is still occurring today. 相似文献