Accurate measurements of the D/H ratio in our Galaxy provide critical tests of Galactic chemical evolution and constrain the primor-dial value of D/H. Very high quality ultraviolet spectra from the GHRS and STIS instruments on HST have been analyzed for lines of sight toward both early and late-type stars and hot white dwarfs. We will summarize the results that are being obtained for D/H along ...

We discuss the role of the electron temperature in abundance determinations in ionized nebulae (planetary nebulae and giant H II regions). We show that, even when observations provide a direct estimate of T e, abundance determinations may sometimes be significantly in error for reasons other than hypothetical temperature fluctuations or uncertainties in ionization correction factors, and we sho...

Gh plays important roles in development, somatic growth and gametogenesis in vertebrates. To determine the physiological role of Gh in reproduction in male teleosts, the expression of genes encoding Gh and the two Gh receptors (Ghrs) during spermatogenesis, and the action of Gh in vitro was examined using the Japanese eel (Anguilla japonica). gh, ghr1 and ghr2 mRNA transcripts were detected in ...

Table 1. Chemical composition of the Martian atmosphere. Spacecraft data are in black, ground-based spectroscopy is in red, spectroscopy from Earthorbiting observatories in blue. Species Mixing ratio Instrument CO2 0.955 GS N2 0.027 Viking/MS Ar 0.016 Viking/MS Ne 2.5 ppm Viking/MS Kr 0.3 ppm Viking/MS Xe 80 ppb Viking/MS H 2.7×10 cm Mariner/UVS O 0.01-0.02 Mariner/UVS O2 (1.2−2)×10 FPI CO 8×10...

We calculated profiles of CIV1550, Si IV 1400, NV1240 and OVI 1035 doublet lines using results of 3D MHD simulations of disc accretion onto young stars with dipole magnetic field. It appeared that our calculations can not reproduce profiles of these lines observed (HST/GHRS-STIS and FUSE) in CTTSs’s spectra. We also found that the theory predicts much larger C IV 1550 line flux than observed (u...

Spectral analysis needs the observation of lines of successive ionization stages in order to evaluate the ionization equilibrium (of a particular species) which is a sensitive indicator for the effective temperature (Teff). Since stars with Teff as high as 100 000K have their flux maximum in the extreme ultraviolet (EUV) wavelength range and due to the high degree of ionization, most of the met...

I discuss recent HST observations and interpretation of low-z Lyα clouds toward nearby Seyferts and QSOs, including their frequency, space density, estimated mass, association with galaxies, and contribution to Ωb. Our HST/GHRS detections of 73 Lyα absorbers with NHI ≥ 10 12.6 cm along 11 sightlines covering pathlength ∆(cz) = 86, 000 km s show f(> NHI) ∝ N −0.6±0.2 HI . A group of strong absor...

We report here the discovery of a chemically peculiar star of the HgMn type as a companion to the classical Cepheid variable SU Cyg. This is the first investigation of a HgMn star in a binary system in which a star of a more advanced evolutionary stage is the primary. The age of the Cepheid provides an estimate to the age of the chemical peculiarities which is independent of the photometric cal...