Search results for "feature"
showing 10 items of 4091 documents
Analyzing the Correlation of Classical and Community-aware Centrality Measures in Complex Networks
2021
International audience; Identifying influential nodes in social networks is a fundamental issue. Indeed, it has many applications, such as inhibiting epidemic spreading, accelerating information diffusion, preventing terrorist attacks, and much more. Classically, centrality measures quantify the node's importance based on various topological properties of the network, such as Degree and Betweenness. Nonetheless, these measures are agnostic of the community structure, although it is a ubiquitous characteristic encountered in many real-world networks. To overcome this drawback, there is a growing trend to design so-called community-aware centrality measures. Although several works investigate…
Evidence that Ultra-High-Energy Gamma Rays are a Universal Feature Near Powerful Pulsars
2021
The highest-energy known gamma-ray sources are all located within 0.5 degrees of extremely powerful pulsars. This raises the question of whether ultra-high-energy (UHE; $>$ 56 TeV) gamma-ray emission is a universal feature expected near pulsars with a high spin-down power. Using four years of data from the High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory, we present a joint-likelihood analysis of ten extremely powerful pulsars to search for UHE gamma-ray emission correlated with these locations. We report a significant detection ($>$ 3$��$), indicating that UHE gamma-ray emission is a generic feature of powerful pulsars. We discuss the emission mechanisms of the gamma rays a…
Morphological Differences in Neuromasts of the Blind Cave Fish <i>Astyanax hubbsi </i>and the Sighted River Fish <i>Astyanax mexica…
1990
Vital staining and scanning electron microscopy were used to study the morphology of superficial neuromasts in the blind cave fish, Astyanax hubbsi, and its sighted congener, <i&
Speleothem records decadal to multidecadal hydroclimate variations in southwestern Morocco during the last millennium
2017
Abstract This study presents the first well-dated high resolution stable isotope ( δ 18 O and δ 13 C ) and trace element (Mg and Sr) speleothem records from southwestern Morocco covering the last 1000 yrs. Our records reveal substantial decadal to multidecadal swings between dry and humid periods, consistent with regional paleorecords with prevailing dry conditions during the Medieval Climate Anomaly (MCA), wetter conditions during the second part of the Little Ice Age (LIA), and a trend towards dry conditions during the current warm period. These coherent regional climate signals suggest common climate controls. Statistical analyses indicate that the climate of southwestern Morocco remaine…
Inferences of dietary preferences of Miocene squirrels (Xerinae, Sciuridae) from the Iberian Peninsula and Namibia using microwear analyses and ename…
2020
In this work, we compared microwear features and enamel thickness from upper molars (M1 and M2) of extinct Xerinae squirrels from the Miocene of Namibia (Vulcanisciurus sp) and the Iberian Peninsula (Atlantoxerus nov. sp. and Heteroxerus rubricati). We also examined the microwear from young and adult specimens of one extant squirrel, Atlantoxerus getulus, to compare it with the extinct species. Both, the microwear features and enamel thickness showed that the Miocene African species presented a more abrasive diet than the Iberian ones.
Controlling Factors of the Climate
1988
Since climate represents the characteristic biospheric conditions at a location or area, it chiefly results from the varying solar and atmospheric moisture and circulation conditions over space and time. Climate at any space or time level is, therefore, represented by certain expressions of the various atmospheric elements, which are concerned with radiation, temperature, sunshine, precipitation and others. The superior impact of the atmosphere upon climate is governed by various factors which control the climate; these climate-controlling factors are, in the widest sense, of a topographical nature (see Sects. 2.1–2.3). Additionally, seasons will be considered as a climate-controlling facto…
Assessment of the SMAP Level-4 Surface and Root-Zone Soil Moisture Product Using In Situ Measurements
2017
International audience; The Soil Moisture Active Passive (SMAP) mission Level-4 Surface and Root-Zone Soil Moisture (L4_SM) data product is generated by assimilating SMAP L-band brightness temperature observations into the NASA Catchment land surface model. The L4_SM product is available from 31 March 2015 to present (within 3 days from real time) and provides 3-hourly, global, 9-km resolution estimates of surface (0-5 cm) and root-zone (0-100 cm) soil moisture and land surface conditions. This study presents an overview of the L4_SM algorithm, validation approach, and product assessment versus in situ measurements. Core validation sites provide spatially averaged surface (root zone) soil m…
Microphysical and radiative characterization of a subvisible midlevel Arctic ice cluod by airborne observations - a case study
2009
During the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR) campaign, which was conducted in March and April 2007, an optically thin ice cloud was observed south of Svalbard at around 3 km altitude. The microphysical and radiative properties of this particular subvisible midlevel cloud were investigated with complementary remote sensing and in situ instruments. Collocated airborne lidar remote sensing and spectral solar radiation measurements were performed at a flight altitude of 2300 m below the cloud base. Under almost stationary atmospheric conditions, the same subvisible midlevel cloud was probed with various in situ sensors roughly 30 min later. <br><br> …
African volcanic emissions influencing atmospheric aerosols over the Amazon rain forest
2018
Long-range transport (LRT) plays an important role in the Amazon rain forest by bringing in different primary and secondary aerosol particles from distant sources. The atmospheric oxidation of dimethyl sulfide (DMS), emitted from marine plankton, is considered an important sulfate source over the Amazon rain forest, with a lesser contribution from terrestrial soil and vegetation sulfur emissions. Volcanic sulfur emissions from Africa could be a source of particulate sulfate to the Amazonian atmosphere upon transatlantic transport but no observations have been published. By using satellite observations, together with ground‑based and airborne aerosol particle observations, this paper provide…
Intense magmatic degassing through the lake of Copahue volcano, 2013–2014
2015
Here we report on the first assessment of volatile fluxes from the hyperacid crater lake hosted within the summit crater of Copahue, a very active volcano on the Argentina-Chile border. Our observations were performed using a variety of in situ and remote sensing techniques during field campaigns in March 2013, when the crater hosted an active fumarole field, and in March 2014, when an acidic volcanic lake covered the fumarole field. In the latter campaign, we found that 566 to 1373 t d -1 of SO 2 were being emitted from the lake in a plume that appeared largely invisible. This, combined with our derived bulk plume composition, was converted into flux of other volcanic species (H 2 O ~ 1098…