The hydration of divalent cations in aqueous solution : an x-ray investigation with isomorphous replacement

The x-ray diffraction patterns of M solns. of the nitrates of Co2+, Ni2 +, Zn2+, Mg2+, Cd2+, and Ca2+ were recorded with an Enraf-Nonius liq . jet diffraction camera. These cations were paired into 4 isomorphous groups based on the similarities of the cation-water distances in their cryst. hydrates. A theoretical expression was derived relating the electron distribution function to the difference in the intensities diffracted by a pair of isomorphous solns., and this function was obtained by calcg. the Fourier transform, using the measured intensities. The resulting electron distribution function exhibited a peak near 2 g, ascribed to the primary hydration layer, and a 2nd, less clear-cut, peak near 4 .ANG., attributed to the secondary hydration layer. Least-squares fits of these peaks yielded primary coordination nos. and cation water distances at 25°, and a secondary coordination no. of 12 ± 2. Cation-water distances were also obtained when minor deviations from isomorphism were taken into account

Galaxy rotation curves: the effect of j x B force

Using the Galaxy as an example, we study the effect of j x B force on the rotational curves of gas and plasma in galaxies. Acceptable model for the galactic magnetic field and plausible physical parameters are used to fit the flat rotational curve for gas and plasma based on the observed baryonic (visible) matter distribution and j x B force term in the static MHD equation of motion. We also study the effects of varied strength of the magnetic field, its pitch angle and length scale on the rotational curves. We show that j x B force does not play an important role on the plasma dynamics in the intermediate range of distances 6-12 kpc from the centre, whilst the effect is sizable for larger r (r > 15 kpc), where it is the most crucial.Comment: Accepted for publication in Astrophysics & Space Science (final printed version, typos in proofs corrected

Modeling the magnetic field in the galactic disk using new rotation measure observations from the Very Large Array

We have determined 194 Faraday rotation measures (RMs) of polarized extragalactic radio sources using new, multi-channel polarization observations at frequencies around 1.4 GHz from the Very Large Array (VLA) in the Galactic plane at 17◦ ≤ l ≤ 63◦ and 205◦ ≤ l ≤ 253◦. This catalog fills in gaps in the RM coverage of the Galactic plane between the Canadian Galactic Plane Survey and Southern Galactic Plane Survey. Using this catalog we have tested the validity of recently-proposed axisymmetric and bisymmetric models of the largescale (or regular) Galactic magnetic field, and found that of the existing models we tested, an axisymmetric spiral model with reversals occurring in rings (as opposed to along spiral arms) best matched our observations. Building on this, we have performed our own modeling, using RMs from both extragalactic sources and pulsars. By developing independent models for the magnetic field in the outer and inner Galaxy, we conclude that in the inner Galaxy, the magnetic field closely follows the spiral arms, while in the outer Galaxy, the field is consistent with being purely azimuthal. Furthermore, the models contain no reversals in the outer Galaxy, and together seem to suggest the existence of a single reversed region that spirals out from the Galactic cente

Magnetic Fields in the Milky Way

This chapter presents a review of observational studies to determine the magnetic field in the Milky Way, both in the disk and in the halo, focused on recent developments and on magnetic fields in the diffuse interstellar medium. I discuss some terminology which is confusingly or inconsistently used and try to summarize current status of our knowledge on magnetic field configurations and strengths in the Milky Way. Although many open questions still exist, more and more conclusions can be drawn on the large-scale and small-scale components of the Galactic magnetic field. The chapter is concluded with a brief outlook to observational projects in the near future.Comment: 22 pages, 5 figures, to appear in "Magnetic Fields in Diffuse Media", eds. E.M. de Gouveia Dal Pino and A. Lazaria

Exploring the Threefold Invisible Universe: Low-Frequency Spectropolarimetry with LOFAR as a Probe of Galactic Magnetism

Contains fulltext : 175872.pdf (publisher's version ) (Open Access)Radboud University, 9 oktober 2017Promotor : Falcke, H.D.E. Co-promotor : Haverkorn, M.V, 140 p

Statistical properties of dwarf novae-type cataclysmic variables: the outburst catalogue

Contains fulltext : 155798.pdf (preprint version ) (Open Access

Magnetic Fields in the Milky Way Halo

Contains fulltext : 141167.pdf (preprint version ) (Open Access