Results 51 to 60 of about 50,755 (263)
Early evolutionary history of the seed
Biological Reviews, EarlyView.ABSTRACT The seed is an essential stage in the life history of gymnospermous and angiospermous plants, facilitating both their survival and dispersal. We reappraise knowledge of the evolutionary history of the gymnospermous seed, from its origin in the late Devonian through to the well‐known end‐Permian extinctions – an interval encompassing the ...
Richard M. Bateman +2 more
wiley +1 more source
The NH Distribution of Hard X-Ray Selected Active Galactic Nuclei in the NEP Field
The Astrophysical JournalX-ray surveys are one of the most unbiased methods for detecting Compton-thick (CT; N _H ≥ 10 ^24 cm ^−2 ) active galactic nuclei (AGN), which are thought to comprise up to 60% of AGN within z ≲ 1.0.
Samantha Creech +11 more
doaj +1 more source
The Astrophysical Journal Letters, 2023 Recent studies have proposed that the nuclear millimeter continuum emission observed in nearby active galactic nuclei (AGNs) could be created by the same population of electrons that gives rise to the X-ray emission that is ubiquitously observed in ...
Claudio Ricci +12 more
doaj +1 more source
Variability and the X-ray/UV ratio of Active Galactic Nuclei [PDF]
, 2010 The observed relation between the X-ray radiation from AGNs, originating in the corona, and the optical/UV radiation from the disk is usually described by the anticorrelation between the UV to X-ray slope alpha_ox and the UV luminosity.
Antonucci, M. +3 more
core +1 more source
Extreme X-Ray Iron Lines in Active Galactic Nuclei
The Astrophysical Journal, 2002 We analyze X-ray spectra of heavily obscured (N_H > 10^{24} cm^{-2}) active galaxies obtained with Chandra, concentrating on the iron K alpha fluorescence line. We measure very large equivalent widths in most cases, up to 5 keV in the most extreme example.
Levenson, N. A. +6 more
openaire +2 more sources
The FEBS Journal, EarlyView.Antifreeze proteins from winter‐active spiders were purified using their affinity for ice. After LC–MSMS characterization, corresponding transcripts were identified. The antifreeze protein folds as a β‐solenoid with a large flat ice‐binding site on one surface and can bind to ice crystals and prevent their growth at −4 °C.
Laurie A. Graham +3 more
wiley +1 more source
The Infrared-X-ray continuum correlation in Active Galactic Nuclei
, 2003 The correlation between the soft X-ray and near infrared emission from AGN is analysed using composite models by the code SUMA. We find new evidences for differences in ranges of parameters which characterize the NLR of Seyfert galaxies and LINERs ...
Campos, P. E. +2 more
core +2 more sources
LOW-MASS ACTIVE GALACTIC NUCLEI WITH RAPID X-RAY VARIABILITY [PDF]
The Astrophysical Journal, 2016 ABSTRACT We present a detailed study of the optical spectroscopic properties of 12 active galactic nuclei (AGNs) with candidate low-mass black holes (BHs) selected by Kamizasa et al. through rapid X-ray variability. The high-quality, echellette Magellan spectra reveal broad Hα emission in all the sources, allowing us to estimate robust ...
Ho, Luis, Kim, Minjin
openaire +2 more sources
Journal of Fish Biology, EarlyView.Abstract In the context of current global change, variations in water temperature are one of the environmental conditions with serious consequences for marine life, including reproductive processes. In the small spotted catshark Scyliorhinus canicula, spermatogenesis occurs in spermatocysts composed of synchronously developing germ cells associated ...
Fabian Jeanne +4 more
wiley +1 more source
The Astrophysical JournalWe present a high-resolution X-ray spectroscopic study of the narrow-line Seyfert 1 galaxy NGC 4051 using two XMM-Newton high-resolution Reflection Grating Spectrometer observations.
Roberto Serafinelli +8 more
doaj +1 more source