Detecting exoplanets with FAST?     

Philippe Zarka  Di Li  Jean-Mathias Grie?meier  Laurent Lamy  Julien N.Girard  Sbastien L.G.Hess  T.Joseph W.Lazio  Gregg Hallinan 《天文和天体物理学研究(英文版)》2019,(2)

We briefly review the various proposed scenarios that may lead to nonthermal radio emissions from exoplanetary systems(planetary magnetospheres, magnetosphere-ionosphere and magnetospheresatellite coupling, and star-planet interactions), and the physical information that can be drawn from their detection. The latter scenario is especially favorable to the production of radio emission above 70 MHz. We summarize the results of past and recent radio searches, and then discuss FAST characteristics and observation strategy, including synergies. We emphasize the importance of polarization measurements and a high duty-cycle for the very weak targets that radio-exoplanets prove to be.  相似文献   

Development versus conservation: evaluation of landscape structure changes in Dem?novská Valley,Slovakia     

KRTI?KA Luděk  TOM?íKOVá Ivana  RAKYTOVá Iveta 《山地科学学报》2018,15(6):1153-1170

This paper presents the changes of landscape structure in the Dem?novská Valley which ranks among the most valuable protected areas of Slovakia. The area was selected on the basis of changes associated with the rapidly growing tourism industry and the rise of an important destination in the center of Low Tatras National Park, Slovakia. To document any changes, we visually interpreted data from aerial and satellite images in three periods(1949, 2007 and 2013) and for predicting future changes we used land use planning documentation. Interpreted data were analyzed using overlay analysis and landscape metrics. Results showed extensive changes in the landscape structure mainly connected with the development of tourism infrastructure. We also identified long-term changes whose causes stem from the transformation of society and forest management in the past. The dynamics and extent of these changes may increase in the future. We propose to stop future development of ski slopes and expansion of related infrastructure, to focus on sustainability and environmentally friendly operation of the existing ski resort and to invest a substantial portion of profits to support projects aimed to preserve surrounding lands and wildlife.  相似文献   

Status and outlook of hiking trails in the central part of the Low Tatra Mountains in Slovakia between 1980–1981 and 2013–2014     

HRN?IAROVá Tatiana  KENDERESSY Pavol  ?PULEROVá Jana  VLACHOVI?OVá Miriam  PISCOVá Veronika  DOBROVODSKá Marta 《山地科学学报》2018,15(8):1615-1632

This study presents a methodology for assessment of the condition of hiking trails (HTs) and their impact zones in the central part of the Low Tatra mountain range, based on comparison of two complex data sets gathered in 33 years apart. The first field investigation was performed in 1980 and 1981, and the second in 2013 and 2014. The main goal was to perform a landscape typology in order to assess the susceptibility of landscape complexes to occurrence of anthropogenic and natural destruction processes and to assess the condition and prospects of HTs and their impacts on the adjacent alpine environment. Landscape complexes were characterised by selected abiotic, biotic and technical parameters of HTs and their impact zones. Due to the high variability of these parameters over the length of the HTs, we had to decide on how to map them. This was done using a square grid with 100 m-sized cells. For each cell with HT, the parameters were assigned the typical value within that cell. In total, 26.3 km of HT were studied, stretching over 266 grid cells. On comparison of the two data sets, it was seen that, 64% (171 grid cells) display a generally positive condition, with 54% (143 grid cells) even exhibiting significant improvement or continuously positive state of their condition. 36% (95 grid cells) were in bad condition, including 3% (9 grid cells) whose state had deteriorated, and 2% (6 grid cells) whose state had significantly deteriorated, in the time between the two assessments.  相似文献   

CT冠状动脉造影应用于急性胸痛临床实践研究进展          下载免费PDF全文

迟雪  赵磊? 《CT理论与应用研究》2019,28(6):747-752

急性胸痛是一个重要的公共卫生问题,它可以造成高昂的医疗成本支出,并显著影响人民健康。急性冠脉综合征是急性胸痛血管性病变的主要原因,影像学检查可以快速、有效地对血管性病变进行排查诊断。本文主要就CT冠状动脉造影在急性胸痛中的临床实践做一综述。   相似文献   

Geochemistry of Sediments from the Lopare Basin (Bosnia and Herzegovina): Implications for Paleoclimate, Paleosalinity, Paleoredox and Provenance     

Aleksandra ?AJNOVI?  Nenad GRBA  Franz NEUBAUER  Milica KA?ANIN-GRUBIN  Ksenija STOJANOVI?  Nenad PETKOVI?  Branimir JOVAN?I?EVI? 《《地质学报》英文版》2020,94(5):1591-1618

A combined inorganic and organic geochemical study was carried out on marls and mudstones collected from the Lower Miocene Lopare Basin, Bosnia and Herzegovina. A total of 46 samples collected from two boreholes, Pot 1 (depth of 193 m) and Pot 3 (depth of 344 m), showed that element abundances like boron (B), lithium (Li), strontium (Sr), uranium (U), chromium (Cr), nickel (Ni), magnesium (Mg), sodium (Na) and calcium (Ca) are much higher than average than in the upper continental crust (UCC). Chemical composition indicates at least two sources: (i) Mesozoic ophiolites occurring in the north of the investigated area, and (ii) dacito-andesitic pyroclastics (Mesozoic to Cenozoic). Lopare Basin sedimentation was influenced by strong evaporation resulting in a partly hypersaline lake, which formed during a warm climatic period, probably during the Miocene Climatic Optimum. A brief episode of humid climate conditions resulted in the basin filling-up and deposition of felsic sediments enriched in thorium (Th). Organic geochemistry shows that the majority of studied sediments contains predominantly immature to marginally mature algal organic matter (OM). The biomarker patterns are generally in agreement with the geological history of the Lopare Basin and inorganic and mineralogical data. Conversely, the molecular distribution of n-alkanes as reliable climatic and δ-MTTC as paleosalinity indicators do not support this conclusion.  相似文献   

Post-fire recovery of Puya raimondii,vegetation and birds in the puna of Huascarán National Park,Perú     

Mery L.SUNI  Giovana P.VADILLO  César ARANA  Enoc JARA-PE?A  Letty SALINAS  M.Estela PONCE  Paul M.RAMSAY 《山地科学学报》2024,(1):20-32

A large fire of 233 ha in Huascarán National Park in Peru provided an opportunity to compare plant and bird responses in burned and nearby unburned zones of the puna. Heights and live diameters of flagship Puya raimondii rosettes(assigned to four broad developmental phases), plant communities(66 species in 24 families and nine growth forms) and bird communities(77 species in six trophic guilds) were monitored after the fire. Although no mortality was observed, Puya raimondii plants were affected...  相似文献   

A simple guideline to apply excitation-emission matrix spectroscopy (EEMs) for the characterization of dissolved organic matter (DOM) in anoxic marine sediments     

Shuchai Gan  Verena B.Heuer  Frauke Schmidt  Lars W?rmer  Kai-Uwe Hinrichs 《海洋学报(英文版)》2023,42(1):109-119

Marine sediments represent a major carbon reservoir on Earth. Dissolved organic matter(DOM) in pore waters accumulates products and intermediates of carbon cycling in sediments. The application of excitation-emission matrix spectroscopy(EEMs) in the analysis of subseafloor DOM samples is largely unexplored due to the redoxsensitive matrix of anoxic pore water. Therefore, this study aims to investigate the interference caused by the matrix on EEMs and propose a guideline to prepare pore water sam...  相似文献   

Ground-borne vibrations induced by impact pile driving: experimental assessment and mitigation measures     

Aires Cola?o  A.M.Abouelmaty  P.Alves Costa 《地震工程与工程振动(英文版)》2023,(1):105-115

Impact pile driving is an interesting technique for the construction of deep foundations from a practical and economical point of view. However, the generalization of this technique can be restricted due to the excessive vibration levels that can be generated, which can be especially problematic in residential areas. However, different mitigation measures can be applied to prevent excessive vibration levels inside buildings located near construction sites. To compare its efficiency through a num...  相似文献   

Macroscopically‐Zoned Grandite from the Garnetite Skarn of Meka Presedla (Kopaonik Mountain,Serbia)     

Pavle Tan?i?  Predrag Vuli?  Reinhard Kaindl  Bernhard Sartory  Radovan Dimitrijevi? 《《地质学报》英文版》2012,86(2):394-405

The macroscopically-zoned grandite from the garnetite skarn of Meka Presedla (Kopaonik Mountain, Serbia) was studied with optical microscopy, electron microprobe analysis (EMPA), Fourier transform infra-red (FT–IR), and Raman methods. The EMPA results indicate that the main core–rim compositional variations (Ca2.93–2.97Mn0.05–0.06Mg0.00–0.01Al1.14–1.26Fe3+0.72–0.83Ti0.00–0.02Si2.97–3.02O12) slightly differ along the zones, showing evidence for a quasi-cyclic alternation of the oscillatory zoning nature. Among this, considerable variation is observed only by the Al–Fe3+ substitutions in the octahedral site. The EMPA also indicate that the grandite zones compositionally vary, mostly within ±1 and ±2 mol% of the homogeneity level range, that is, Grs64±1Adr36±1Sps2 (A), Grs62±1Adr38±1Sps2 (B), Grs59±2Adr40±2Sps2 (C), Grs58±2Adr41±2Sps2 (D), and Grs58±1Adr41±1Sps2 (E). Therefore, the investigated garnet can be considered as relatively highly homogeneous. The majority of compositions lie within the narrow miscibility region of 0.58±2相似文献   

Crystal Structure and Chemical Composition of Ludwigite from Vranovac Ore Deposit (Boranja Mountain,Serbia)     

Pavle TAN?I?  Radovan DIMITRIJEVI?  Maja POZNANOVI?  Aleksandar PA?EVSKI  Slobodanka SUDAR 《《地质学报》英文版》2012,86(6):1524-1538

The crystal structure of ludwigite from Vranovac ore deposit (Boranja Mt., Serbia) was refined using the X-ray powder diffraction (XRPD) Rietveld method in the space group Pbam to a final RB=7.45% and RF=5.26%. It has the unit cell dimensions of: a=9.2515(2) ?; b=12.3109(2) ?; c=3.03712(7) ?; and V=345.91(1) ?3. The calculated distances and angles are mostly in good agreement with the Mg2+-Fe2+ substitutions across the M(1) and M(3) sites, as well as with the Fe3+-Al3+ replacement in the M(4) site. However, the mean observed M(2)-O distance is considerably shorter than prescribed, due to a slight increase of the Fe3+ content in the M(2) site. Such replacement was compensated by slight increase of the Fe2+ content in the M(4) site, resulting in the (Mg1.48Fe2+0.46Fe3+0.05Mn0.02)2.01(Fe3+0.94Fe2+0.04Al0.02)1.00B1.00O5 composition. The formation temperature was estimated to be about 500–600°C. The influences of the various chemical compositions to the crystallographic parameters, M-O distances, M(3) and M(4) sites shift, distortion parameters and estimated valences, were also studied and compared with other reference samples.  相似文献