Search for a Periodic Signal in the Emission from the Crab Nebula at High Energies     

Nizamov  B. A.  Pshirkov  M. S. 《Astronomy Letters》2021,47(2):88-93

Astronomy Letters - The emission from the Crab nebula exhibits a significant gamma-ray variability. In this paper we have analyzed this variability in terms of periodicity. Using the pulsar...  相似文献   

Do mixing models with different input requirement yield similar streamflow source contributions? Case study: A tropical montane catchment     

Jorge Ramón  Alicia Correa  Edison Timbe  Giovanny M. Mosquera  Enma Mora  Patricio Crespo 《水文研究》2021,35(6):e14209

Hydrogeochemical based mixing models have been successfully used to investigate the composition and source identification of streamflow. The applicability of these models is limited due to the high costs associated with data collection and the hydrogeochemical analysis of water samples. Fortunately, a variety of mixing models exist, requiting different amount of data as input, and in data scarce regions it is likely that preference will be given to models with the lowest requirement of input data. An unanswered question is if models with high or low input requirement are equally accurate. To this end, the performance of two mixing models with different input requirement, the mixing model analysis (MMA) and the end-member mixing analysis (EMMA), were verified on a tropical montane headwater catchment (21.7 km²) in the Ecuadorian Andes. Nineteen hydrogeochemical tracers were measured on water samples collected weekly during 3 years in streamflow and eight potential water sources or end-members (precipitation, lake water, soil water from different horizons and springs). Results based on 6 conservative tracers, revealed that EMMA (using all tracers) and MMA (using pair-combinations out of the 6 conservative ones), identified the same end-members: rainfall, soil water and spring water., as well as, similar contribution fractions to streamflow from rainfall 21.9% and 21.4%, soil water 52.7% and 52.3%, and spring water 26.1% and 28.7%, respectively. Our findings show that a hydrogeochemical mixing model requiring a few tracers can provide similar outcomes than models demanding more tracers as input data. This underlines the value of a preliminary detailed hydrogeochemical characterization as basis to derive the most cost-efficient monitoring strategy.  相似文献   

The information system of the French Peatland Observation Service: Service National d'Observation Tourbières – A valuable tool to assess the impact of global changes on the hydrology and biogeochemistry of temperate peatlands through long term monitoring     

Sébastien Gogo  Jean-Baptiste Paroissien  Fatima Laggoun-Défarge  Jean-Marc Antoine  Léonard Bernard-Jannin  Guillaume Bertrand  Philippe Binet  Stéphane Binet  Guillaume Bouger  Yohann Brossard  Thierry Camboulive  Jean-Pierre Caudal  Stéphane Chevrier  Geneviève Chiapiuso  Benoît D'Angelo  Pilar Durantez  Chris Flechard  André-Jean Francez  Didier Galop  Laure Gandois  Daniel Gilbert  Christophe Guimbaud  Louis Hinault  Adrien Jacotot  Franck Le Moing  Emilie Lerigoleur  Gaël Le Roux  Fabien Leroy  Alexandre Lhosmot  Qian Li  Elodie Machado Da Silva  Jean-Sébastien Moquet  Juanita Mora-Gomez  Laurent Perdereau  Thomas Rosset  Marie-Laure Toussaint 《水文研究》2021,35(6):e14244

Mitigating and adapting to global changes requires a better understanding of the response of the Biosphere to these environmental variations. Human disturbances and their effects act in the long term (decades to centuries) and consequently, a similar time frame is needed to fully understand the hydrological and biogeochemical functioning of a natural system. To this end, the ‘Centre National de la Recherche Scientifique’ (CNRS) promotes and certifies long-term monitoring tools called national observation services or ‘Service National d'Observation’ (SNO) in a large range of hydrological and biogeochemical systems (e.g., cryosphere, catchments, aquifers). The SNO investigating peatlands, the SNO ‘Tourbières’, was certified in 2011 ( https://www.sno-tourbieres.cnrs.fr/ ). Peatlands are mostly found in the high latitudes of the northern hemisphere and French peatlands are located in the southern part of this area. Thus, they are located in environmental conditions that will occur in northern peatlands in coming decades or centuries and can be considered as sentinels. The SNO Tourbières is composed of four peatlands: La Guette (lowland central France), Landemarais (lowland oceanic western France), Frasne (upland continental eastern France) and Bernadouze (upland southern France). Thirty target variables are monitored to study the hydrological and biogeochemical functioning of the sites. They are grouped into four datasets: hydrology, fluvial export of organic matter, greenhouse gas fluxes and meteorology/soil physics. The data from all sites follow a common processing chain from the sensors to the public repository. The raw data are stored on an FTP server. After operator or automatic processing, data are stored in a database, from which a web application extracts the data to make them available ( https://data-snot.cnrs.fr/data-access/ ). Each year at least, an archive of each dataset is stored in Zenodo, with a digital object identifier (DOI) attribution ( https://zenodo.org/communities/sno_tourbieres_data/ ).  相似文献   

Transient AT2018cow: A Scenario with an Equatorial Disk     

Urvachev  E. M.  Blinnikov  S. I.  Nomoto  K. 《Astronomy Letters》2021,47(11):738-745

Astronomy Letters - To explain the presence of early X-ray emission from the object AT2018cow, we have studied a scenario with the presence of dense ejecta in the system in the equatorial plane....  相似文献   

New Orbit and Estimate of the Mass of the Star 61 Cygni Based on Observations of it in 1819-2019     

Izmailov  I. S.  Shakht  N. A.  Polyakov  E. V.  Gorshanov  D. L.  Pogodin  M. A. 《Astrophysics》2021,64(2):160-171

Astrophysics - This paper is a continuation of our earlier work devoted to determining the orbit and mass of the star 61 Cyg and the changes in the photometric characteristics of its components....  相似文献   

The GEOMON network of Czech catchments provides long-term insights into altered forest biogeochemistry: From acid atmospheric deposition to climate change     

Filip Oulehle  Milan Fischer  Jakub Hruška  Tomáš Chuman  Pavel Krám  Tomáš Navrátil  Miroslav Tesař  Miroslav Trnka 《水文研究》2021,35(5):e14204

In 1994, a network of small catchments (GEOMON) was established in the Czech Republic to determine input–output element fluxes in semi-natural forest ecosystems recovering from anthropogenic acidification. The network consists from 16 catchments and the primary observations of elements fluxes were complemented by monitoring of biomass stock, element pools in soil and vegetation, and the main water balance components. Over last three decades, reductions of SO₂, NO_x and NH₃ emissions were followed by sulphur (S) and nitrogen (N) deposition reductions of 75% and 30%, respectively. Steeper declines of strong acid anion concentrations compared to cations (Ca, Mg, Na, K, NH₄) in precipitation resulted in precipitation pH increase from 4.5 to 5.2 in bulk precipitation and from 4.0 to 5.1 in spruce throughfall. Stream chemistry responded to changes in deposition: S leaching declined. However at majority of catchments soils acted as a net source of S to runoff, delaying recovery. Stream pH increased at acidic streams (pH < 6) and aluminium concentration decreased. Stream nitrate (NO₃) concentration declined by 60%, considerably more than N deposition. Stream NO₃ concentration was tightly positively related to stream total dissolved nitrogen to total phosphorus (P) ratio, suggesting the role of P availability on N retention. Trends in dissolved organic carbon fluxes responded to both acidification recovery and to runoff temporal variation. An exceptional drought occurred between 2014 and 2019. Over this recent period, streamflow decreased by ≈ 40% on average compared to 1990s, due to the increases of soil evaporation and vegetation transpiration by ≈ 30% and declines in precipitation by ≈ 15% on average across the elevational gradient. Sharp decreases of stream runoff at catchments <650 m a.s.l. corresponded to areas of recent forest decline caused by bark beetle infestation on drought stressed spruce forests. Understanding of the interactions among legacies of acidification and eutrophication, drought effects on the water cycle and forest disturbance dynamics is requisite for effective management of forested ecosystems under anthropogenic influence.  相似文献   

Determination of the Thermophysical Characteristics of the Lunar Soil Using Solar Heat     

Dudkin  K. K.  Alifanov  O. M. 《Solar System Research》2020,54(7):630-636

Solar System Research - The possibility of determining the thermophysical characteristics of the lunar soil by a penetrating probe when using solar heat as a heater is considered. The effectiveness...  相似文献   

Early Quaternary Age of the Final Stage of Volcanism in the Central Part of the Sredinny Range of Kamchatka (K–Ar Data)     

Pevzner  M. M.  Lebedev  V. A.  Kuscheva  Yu. V.  Volynets  A. O.  Tolstykh  M. L.  Babansky  A. D. 《Doklady Earth Sciences》2020,490(1):1-3

Doklady Earth Sciences - A first set of K–Ar isotopic ages obtained, which allowed to estimate the age of the largest volcanoes of the Anaunsky Dol (3.2, 2.2 and 1.9 Ma) and eruptive centers...  相似文献   

Radiative Instability of a Barotropic Jet Flow in a Rotating Stratified Atmosphere     

Kalashnik  M. V. 《Izvestiya Atmospheric and Oceanic Physics》2019,55(3):229-234

Izvestiya, Atmospheric and Oceanic Physics - This paper investigates the stability of a jet flow with a piecewise linear velocity profile in a rotating stratified atmosphere. The linearized set of...  相似文献   

The Magma Feeding System of the Klyuchevskaya Group of Volcanoes (Kamchatka)     

Gordeev  E. I.  Koulakov  I. Yu.  Shapiro  N. M. 《Doklady Earth Sciences》2020,493(2):627-631

Doklady Earth Sciences - Using observations from a large-scale seismic station network, we built a seismic tomography model of velocity anomalies for longitudinal (P-wave) and transverse (S-wave)...  相似文献