Interferometric Observations of the Quiet Sun at 20 and 25 MHz in May 2014

© 2018, Springer Nature B.V. We present the results of solar observations at 20 and 25 MHz with the Ukrainian T-shaped Radio telescope of the second modification (UTR-2) in the interferometric session from 27 May to 2 June 2014. In this case, the different baselines 225, 450, and 675 m between the sections of the east–west and north–south arms of UTR-2 were used. On 29 May 2014, strong sporadic radio emission consisting of Type III, Type II, and Type IV bursts was observed. On other days, there was no solar radio activity in the decameter range. We discuss the observation results of the quiet Sun. Fluxes and sizes of the Sun in east–west and north–south directions were measured. The average fluxes were 1050 – 1100 Jy and 1480 – 1570 Jy at 20 and 25 MHz, respectively. The angular sizes of the quiet Sun in equatorial and polar directions were 55 ′ and 49 ′ at 20 MHz and 50 ′ and 42 ′ at 25 MHz. The brightness temperatures of the radio emission were Tb=5.1×105K and Tb=5.7×105K at 20 and 25 MHz, respectively.status: publishe

The Unique DNA Sequences Underlying Equine Centromeres

Centromeres are highly distinctive genetic loci whose function is specified largely by epigenetic mechanisms. Understanding the role of DNA sequences in centromere function has been a daunting task due to the highly repetitive nature of centromeres in animal chromosomes. The discovery of a centromere devoid of satellite DNA in the domestic horse consolidated observations on the epigenetic nature of centromere identity, showing that entirely natural chromosomes could function without satellite DNA cues. Horses belong to the genus Equus which exhibits a very high degree of evolutionary plasticity in centromere position and DNA sequence composition. Examination of horses has revealed that the position of the satellite-free centromere is variable among individuals. Analysis of centromere location and composition in other Equus species, including domestic donkey and zebras, confirms that the satellite-less configuration of centromeres is common in this group which has undergone particularly rapid karyotype evolution. These features have established the equids as a new mammalian system in which to investigate the molecular organization, dynamics and evolutionary behaviour of centromeres