Abstract In Fe 3 O 4 nanopowders were carried out microwave absorption measurements at X-band (8.8-9.8 GHz), in the 89-300 K temperature range, by means of ferromagnetic resonance (FMR), magnetically modulated spectroscopy (MAMMAS) and low-field (LFMA). The Verwey transition around T v ∼ 137 has been detected employed FMR parameters: resonant field ( H res ) linewidth ΔH pp ), as function. MAMM...

We study the density field around zem > 4 quasars using high quality medium spectral resolution ESI-Keck spectra (R ∼ 4300, SNR > 25) of 45 high-redshift quasars selected from a total of 95 spectra. This large sample considerably increases the statistics compared to previous studies. The redshift evolution of the mean photo-ionization rate and the median optical depth of the intergalactic mediu...

Accretion disks are observed in young stars, cataclysmic variables, binary X-ray sources et al. Accretion disk theory was first developed as a theory with the local heat balance, where the whole energy produced by a viscous heating was emitted to the sides of the disk. Important part of this theory was the phenomenological treatment of the turbulent viscosity, known the “ alpha” prescription, w...

We present new X-ray and optical spectroscopy of a Type 2 quasar candidate selected from a follow-up program of hard, optically-dim, serendipitous Chandra sources. The source is confirmed to be a Type 2 quasar at z = 0.536 with an intrinsic 2–10 keV luminosity L 2−10 = 5 × 10 44 h −2 0.7 erg s −1 , an absorbing column density N H = 8 × 10 23 cm −2 and a neutral Fe Kα line detected by XMM-Newton...