南极菲尔德斯半岛海鸟与种群分布   总被引：4，自引：2，他引：2       下载免费PDF全文

王自磐  Simone Pfeiffer 《极地研究》2004,16(4):271-280

2000/2001-2002/2003南极夏季期间,对中国南极长城站所在地乔治王岛菲尔德斯半岛及邻近区海鸟群落组成与种群分布特征进行了观测研究。本文报道了对该地区三次考察期间记录的海鸟共11科25种。其中,有繁殖活动的海鸟12种,优势种有白眉企鹅(Pygoscelispapua)和黄蹼洋海燕(Oceanitesoceanicus),常见种有纹颊企鹅(Pygoscelisantarctica)、巨鹱(Macronectesgiganteus)、花斑鹱(Daptioncapenis)、南极燕鸥(Sternavittata)和灰贼鸥(Catharactaantarctica)等。  相似文献   

Northwest Africa 6232: Visible–near infrared reflectance spectra variability of an olivine diogenite     

Cristian Carli  Giovanni Pratesi  Vanni Moggi-Cecchi  Francesca Zambon  Fabrizio Capaccioni  Simone Santoro 《Meteoritics & planetary science》2018,53(10):2228-2242

Visible and near-infrared (VNIR) reflectance is an important spectroscopic technique to identify minerals, and their associations, on planetary body surfaces. Howardites, eucrites, and diogenites (HED) are a class of igneous-like meteorites whose genetic connection with asteroid 4 Vesta has since long been inferred and recently confirmed by Dawn mission results. Pyroxene and olivine are the two major mafic minerals present in HED which can be identified with VNIR reflectance measurements. Thus, studying the compositional variability of those phases and their mixtures by means of laboratory spectroscopic measurements on different diogenitic or eucritic samples is one of the prime methods to better understand the evolution of 4 Vesta's crust. Here, we report the VNIR reflectance spectral analysis of a harzburgitic olivine diogenite, Northwest Africa 6232 (probably paired with Northwest Africa 5480), containing variable amounts of olivine as small grains or aggregates. We found that the olivine diogenite spectral parameters (e.g., band position) of powdered samples and polished slabs are in agreement. Moreover, the olivine diogenite band position shifts from synthetic orthopyroxene in accordance with the presence of olivine and chromite. In particular, the presence of a large olivine clast permits us to determine a linear variation of the band position from synthetic orthopyroxene and olivine, but underestimates the presence of olivine in the olivine diogenite spot.  相似文献   

Geant4 simulations of soft proton scattering in X-ray optics     

Valentina?Fioretti  Teresa?Mineo  Andrea?Bulgarelli  Paolo?Dondero  Vladimir?Ivanchenko  Fan?Lei  Simone?Lotti  Claudio?Macculi  Alfonso?Mantero 《Experimental Astronomy》2017,44(3):413-435

Low energy protons (< 300 keV) can enter the field of view of X-ray telescopes, scatter on their mirror surfaces at small incident angles, and deposit energy on the detector. This phenomenon can cause intense background flares at the focal plane decreasing the mission observing time (e.g. the XMM-Newton mission) or in the most extreme cases, damaging the X-ray detector. A correct modelization of the physics process responsible for the grazing angle scattering processes is mandatory to evaluate the impact of such events on the performance (e.g. observation time, sensitivity) of future X-ray telescopes as the ESA ATHENA mission. The Remizovich model describes particles reflected by solids at glancing angles in terms of the Boltzmann transport equation using the diffuse approximation and the model of continuous slowing down in energy. For the first time this solution, in the approximation of no energy losses, is implemented, verified, and qualitatively validated on top of the Geant4 release 10.2, with the possibility to add a constant energy loss to each interaction. This implementation is verified by comparing the simulated proton distribution to both the theoretical probability distribution and with independent ray-tracing simulations. Both the new scattering physics and the Coulomb scattering already built in the official Geant4 distribution are used to reproduce the latest experimental results on grazing angle proton scattering. At 250 keV multiple scattering delivers large proton angles and it is not consistent with the observation. Among the tested models, the single scattering seems to better reproduce the scattering efficiency at the three energies but energy loss obtained at small scattering angles is significantly lower than the experimental values. In general, the energy losses obtained in the experiment are higher than what obtained by the simulation. The experimental data are not completely representative of the soft proton scattering experienced by current X-ray telescopes because of the lack of measurements at low energies (< 200 keV) and small reflection angles, so we are not able to address any of the tested models as the one that can certainly reproduce the scattering behavior of low energy protons expected for the ATHENA mission. We can, however, discard multiple scattering as the model able to reproduce soft proton funnelling, and affirm that Coulomb single scattering can represent, until further measurements at lower energies are available, the best approximation of the proton scattered angular distribution at the exit of X-ray optics.  相似文献   

Ultrastructure and dispersal potential of sponge larvae: tufted versus evenly ciliated parenchymellae     

Maria J. Uriz  Xavier Turon  & Simone Mariani 《Marine Ecology》2008,29(2):280-297

In this work we analyse the ultrastructure and behaviour of two representative types of parenchymella sponge larvae: the evenly ciliated larva of Scopalina lophyropoda , and the tufted larva of Cacospongia mollior . We sought to find correlates of the dispersal abilities and distribution patterns of these species. Laboratory experiments were performed under two different conditions of water movement (still water and a slight oscillatory movement), and at different times of the larval life-span. Larvae of S. lophyropoda were motionless most of the time, maintaining a vertical posture and rotating on their main axis, and they did not respond to directional light. Larvae of C. mollior were active swimmers that responded negatively to light stimuli. In both cases, movement decreased as the larval age increased. Ultrastructurally, C. mollior larvae were more compact, with more reserves and abundant collagen bundles. Desmosome-like structures were seen connecting the apical parts of the ciliated surface in both species. Two different types of putative light-sensitive structures were found. Both structural and behavioural characteristics favour a greater dispersal capability for C. mollior and a philopatric dispersal mode for S. lophyropoda . These predictions are in agreement with the observed ecological distribution of the species.  相似文献   

On singularity and the elusiveness of urban form. A commentary on Tariq Jazeel's ‘Singularity. A manifesto for incomparable geographies’     

AbdouMaliq Simone 《Singapore journal of tropical geography》2019,40(1):22-25

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Comparing Beerkan infiltration tests with rainfall simulation experiments for hydraulic characterization of a sandy‐loam soil          下载免费PDF全文

Simone Di Prima  Vincenzo Bagarello  Laurent Lassabatere  Rafael Angulo‐Jaramillo  Inmaculada Bautista  Maria Burguet  Artemi Cerdà  Massimo Iovino  Massimo Prosdocimi 《水文研究》2017,31(20):3520-3532

Saturated soil hydraulic conductivity, K _s , data collected by ponding infiltrometer methods and usual experimental procedures could be unusable for interpreting field hydrological processes and particularly rainfall infiltration. The K _s values determined by an infiltrometer experiment carried out by applying water at a relatively large distance from the soil surface could however be more appropriate to explain surface runoff generation phenomena during intense rainfall events. In this study, a link between rainfall simulation and ponding infiltrometer experiments was established for a sandy‐loam soil. The height of water pouring for the infiltrometer run was chosen, establishing a similarity between the gravitational potential energy of the applied water, E _p , and the rainfall kinetic energy, E _k . To test the soundness of this procedure, the soil was sampled with the Beerkan estimation of soil transfer parameters procedure of soil hydraulic characterization and two heights of water pouring (0.03 m, i.e., usual procedure, and 0.34 m, yielding E _p  = E _k ). Then, a comparison between experimental steady‐state infiltration rates, i _sR , measured with rainfall simulation experiments determining runoff production and K _s values for the two water pouring heights was carried out in order to discriminate between theoretically possible (i _sR  ≥ K _s ) and impossible (i _sR  < K _s ) situations. Physically possible K _s values were only obtained by applying water at a relatively large distance from the soil surface, because i _sR was equal to 20.0 mm h^?1 and K _s values were 146.2–163.9 and 15.2–18.7 mm h^?1 for a height of water pouring of 0.03 and 0.34 m, respectively. This result suggested the consistency between Beerkan runs with a high height of water pouring and rainfall simulator experiments. Soil compaction and mechanical aggregate breakdown were the most plausible physical mechanisms determining reduction of K _s with height. This study demonstrated that the height from which water is poured onto the soil surface is a key parameter in infiltrometer experiments and can be adapted to mimic the effect of high intensity rain on soil hydraulic properties.  相似文献   

Additive effects of climate change and human hunting explain population decline and extinction in cave bears     

Alessandro Mondanaro  Mirko Di Febbraro  Marina Melchionna  Francesco Carotenuto  Silvia Castiglione  Carmela Serio  Simone Danisi  Lorenzo Rook  Jose Alexandre F. Diniz‐Filho  Pasquale Raia 《Boreas: An International Journal of Quaternary Research》2019,48(3):605-615

Cave bears (Ursus spelaeus) are an iconic component of the European late Quaternary Ice Age megafauna. Recent demographic analyses based on cave bear mtDNA sequences and refined radiocarbon dating indicate that cave bear population size and genetic diversity started to decline some 50 kilo years ago (kya). Hence, neither the coldest phase of the last glaciation (started some 24 kya), nor the colonization of Europe by Palaeolithic hunters (started some 45 kya) coincides with the beginning of population decline. Here, we reconstructed cave bear climatic niche evolution through time. Then, we performed spatially explicit population viability analyses to assess cave bear demographics through time in response to climatic changes, human effects on bear survival and their combination. We found that climate change was responsible for a 10‐fold decrease in cave bear population size after 40 kya. However, climate change on its own could not explain U. spelaeus extinction at 24 kya. Additional negative effects consistent with human population expansion are required to explain both U. spelaeus' retreat from eastern Europe since 40 kya and its final extinction.  相似文献   

Moving beyond run‐off calibration—Multivariable optimization of a surface–subsurface–atmosphere model          下载免费PDF全文

Simon Stisen  Julian Koch  Torben O. Sonnenborg  Jens Christian Refsgaard  Simone Bircher  Rasmus Ringgaard  Karsten H. Jensen 《水文研究》2018,32(17):2654-2668

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Validation of Geant4 10.3 simulation of proton interaction for space radiation effects     

Vladimir Ivanchenko  Paolo Dondero  Valentina Fioretti  Anton Ivantchenko  Fan Lei  Simone Lotti  Alfonso Mantero  Teresa Mineo 《Experimental Astronomy》2017,44(3):437-450

Monte Carlo simulation of space radiation effects induced by protons is important for design of space missions. Geant4 is a well established toolkit for Monte Carlo simulation focused on high energy physics applications. In this work, a set of new validation results versus data for Geant4 electromagnetic and hadronic interaction of protons is presented and discussed. Optimal configuration of Geant4 physics for space applications is proposed.  相似文献   

Importance of orientation to the sun and local landscape features in young inexpert Talitrus saltator (Amphipoda: Talitridae) from two Italian beaches differing in morphodynamics,erosion or stability     

Simone Gambineri  Felicita Scapini 《Estuarine, Coastal and Shelf Science》2008

Juvenile sandhoppers (Talitrus saltator Montagu 1808; Crustacea: Amphipoda) were tested under natural conditions to examine their ability to orient to the sun and local features. Experiments were carried out on two Italian sandy beaches subject to different geomorphological dynamics, one under erosion from the sea and the other one under morphodynamic equilibrium (between erosion and accretion). Laboratory-born samples of each population were tested on their beach of origin and compared with wild individuals of the same age; other laboratory-born samples were tested on both beaches, that of origin and the other beach. The population from the beach displaying geomorphologic equilibrium, oriented seawards on both beaches, referring to the sun and the local landscape, while the population from the beach under erosion tended to orient to prominent landscape features on both beaches displaying a scototaxis. These results showed the importance of orientation to local landscape features in young inexpert talitrids, and the innateness of this behaviour in natural populations when shoreline stability allows for a genetic stabilisation of orientation mechanisms.  相似文献