We present the results of high velocity (1.3 km s channels) and high spatial (∼5, or ∼ 250 pc at the distance of I Zw 18) resolution HI synthesis observations of the blue compact dwarf galaxy I Zw 18 to investigate the link between its unique evolutionary history and the neutral gas distribution and kinematics. The HI distribution is extensive, with diffuse neutral gas extending to the northwes...

We present results based on an XMM-Newton observation of the prototype narrow-line Seyfert 1 galaxy I Zw 1 performed in June 2002. The 0.6−12 keV spectrum is well described by a steep power-law (Γ ∼ 2.3) and a weak soft blackbody component (kT ∼ 200 eV) below 2 keV. The soft X-ray excess emission is featureless and contributes only ∼ 10% to the total X-ray emission in the 0.6− 2 keV band. There...

In this paper we study the linearizability problem of the two-dimensional complex quasi-cubic system ż = z + (zw)(a30z + a21zw + a12zw + a03w), ẇ = −w − (zw)(b30w + b21wz+b12wz +b03z), where z,w, ai j, bi j ∈ C and d is a real number. We find a transformation to change the quasi-cubic system into an equivalent quintic system and then obtain the necessary and sufficient linearizability condition...

Sex chromosome dosage compensation balances homogametic sex chromosome expression with autosomal expression in the heterogametic sex, leading to sex chromosome expression parity between the sexes. If compensation is incomplete, this can lead to expression imbalance and sex-biased gene expression. Recent work has uncovered an intriguing and variable pattern of dosage compensation across species ...

Most of our knowledge of sex-chromosome evolution comes from male heterogametic (XX/XY) taxa. With the genome sequencing of multiple female heterogametic (ZZ/ZW) taxa, we can now ask whether there are patterns of evolution common to both sex chromosome systems. In all XX/XY systems examined to date, there is an excess of testis-biased retrogenes moving from the X chromosome to the autosomes, wh...

The short-term spectral variability of the narrow-line Seyfert 1 galaxy I Zwicky 1 (I Zw 1) as observed in an 85 ks XMM-Newton observation is discussed in detail. I Zw 1 shows distinct modes of variability prior to and after a flux dip in the broad-band light curve. Before the dip the variability can be described as arising from changes in shape and normalisation of the spectral components. Onl...

The peculiar cytology and unique evolution of sex chromosomes raise many fundamental questions. Why and how sex chromosomes evolved has been debated over a century since H.J. Muller suggested that sex chromosome pairs evolved ultimately from a pair of autosomes. This theory was adapted to explain variations in the snake ZW chromosome pair and later the mammal XY. S. Ohno pointed out similaritie...

Sticklebacks are small fish that inhabit fresh water and marine environments throughout the Northern Hemisphere. They are established models for the study of species evolution (speciation) and are more recent subjects for the study of chromosome rearrangements, as the chromosomes of the six species within the stickleback family differ in both number and morphology (shape/size). These difference...

Pleurodeles waltl is a newt with a ZZ male-ZW female sex determination mechanism, and a temperature-sensitive gonadal sex differentiation. Raising larvae at 32 degrees C from stage 42 to stage 54 (thermosensitive period) drives genetic females to differentiate into functional males. Estrogens are intimately linked with temperature action in this species, as well as in other vertebrates with tem...

Effects of Sex Ratio Organism (SRO) on the development of embryonic cells of Drosophila melanogaster were studied in vitro. The single embryo culture technique and a histochemical staining method were employed to distinguish male embryo cultures from female ones. SRO-infected Zw(n) females were crossed to wild-type males, and their embryos were separately dissociated and cultured in vitro. Cell...