What can we say about seed fields for galactic dynamos?

We demonstrate that a quasi-uniform cosmological seed field is a much less suitable seed for a galactic dynamo than has often been believed. The age of the Universe is insufficient for a conventional galactic dynamo to generate a contemporary galactic magnetic field starting from such a seed, accepting conventional estimates for physical quantities. We discuss modifications to the scenario for the evolution of galactic magnetic fields implied by this result. We also consider briefly the implications of a dynamo number that is significantly larger than that given by conventional estimates

Magnetic field reversals and galactic dynamos

We argue that global magnetic field reversals similar to those observed in the Milky Way occur quite frequently in mean-field galactic dynamo models that have relatively strong, random, seed magnetic fields that are localized in discrete regions. The number of reversals decreases to zero with reduction of the seed strength, efficiency of the galactic dynamo and size of the spots of the seed field. A systematic observational search for magnetic field reversals in a representative sample of spiral galaxies promises to give valuable information concerning seed magnetic fields and, in this way, to clarify the initial stages of galactic magnetic field evolution

Testing the cosmological evolution of magnetic fields in galaxies with the SKA

We investigate the cosmological evolution of large- and small-scale magnetic fields in galaxies at high redshifts. Results from simulations of hierarchical structure formation cosmology provide a tool to develop an evolutionary model of regular magnetic fields coupled to galaxy formation and evolution. Turbulence in protogalactic halos generated by thermal virialization can drive an efficient turbulent dynamo. The mean-field dynamo theory is used to derive the timescales of amplification and ordering of regular magnetic fields in disk and dwarf galaxies. For future observations with the SKA, we predict an anticorrelation at fixed redshift between galaxy size and the ratio between ordering scale and galaxy size. Undisturbed dwarf galaxies should host fully coherent fields at z<1, spiral galaxies at z<0.5.Comment: 2 pages, contribution to the proceedings of the IAU Symposium 259 "Cosmic Magnetic Fields: from Planets, to Stars and Galaxies", Puerto Santiago, Tenerife, Spain, November 3-7, 2008 (in press

Patterns of Floral Structure and Orientation in Japonolirion , Narthecium, and Tofieldia

Floral evolution requires reassessment in basal monocots, including species formerly assigned to Melanthiaceae, in the light of recent developments in the molecular phylogenetics of monocots. We have investigated flowers of Tofieldia (Tofieldiaceae), Japonolirion (Petrosaviaceae), and Narthecium (Nartheciaceae). We confirm Engler\u27s (1888) hypothesis that orientation of lateral flowers in monocots is dependent on presence and position of additional phyllomes on the pedicel. The type of floral orientation that occurs in Tofieldia is unusual for monocots, since the additional phyllomes are represented by calyculus scales rather than a bracteole, and the outer whorl tepals are initiated alternating with the calyculus scales. In Japonolirion and Narthecium, a bracteole is inserted in an adaxialtransverse or transverse position; either the outer median tepal is adaxial or no single tepal is inserted in the median position. In Tofieldia, the pedicel has a calyculus of an abaxial and two adaxialtransverse phyllomes; the outer median tepal is adaxial. Additional phyllomes on the pedicel are not adaxial, in contrast to adaxial prophylls in the vegetative regions. The presence or absence of a bracteole or calyculus is taxonomically important. Tofieldia pusilla differs from the other species of Tofieldia examined in the absence of a flower-subtending bract, but the calyculus demonstrates some bract-like features in position, structure and development, which can be interpreted as a hybridization of developmental pathways. The abaxial calyculus scale of T. coccinea is delayed in development

Magnetic arms of NGC6946 traced in the Faraday cubes at low radio frequencies

Magnetic fields in galaxies exist on various spatial scales. Large-scale magnetic fields are thought to be generated by the $\alpha-\Omega$ dynamo. Small-scale galactic magnetic fields (1 kpc and below) can be generated by tangling the large-scale field or by the small-scale turbulent dynamo. The analysis of field structures with the help of polarized radio continuum emission is hampered by the effect of Faraday dispersion (due to fluctuations in magnetic field and/or thermal electron density) that shifts signals from large to small scales. At long observation wavelengths large-scale magnetic fields may become invisible, as in the case of spectro-polarimetric data cube of the spiral galaxy NGC~6946 observed with the Westerbork Radio Synthesis Telescope in the wavelength range 17-23 cm. The application of RM Synthesis alone does not overcome this problem. We propose to decompose the Faraday data cube into data cubes at different spatial scales by a wavelet transform. Signatures of the `magnetic arms' observed in NGC~6946 at shorter wavelengths become visible. Our method allows us to search for large-scale field patterns in data cubes at long wavelengths, as provided by new-generation radio telescopes.Comment: 7 pages, 7 figures, 1 tabl

The First Genome from the Basal Monocot Family Has Been Misnamed: Taxonomic Identity of Acorus tatarinowii (Acoraceae), a Source of Numerous Chemical Compounds of Pharmaceutical Importance

The basalmost monocot genus Acorus is well-known for its use in traditional oriental medicine. It comprises the groups of A. calamus and A. gramineus. A recent study recognized three species in the latter group, A. gramineus, A. macrospadiceus, and A. tatarinowii. The material currently known as A. tatarinowii has been extensively studied as a source of various chemical compounds and for producing the first published genome of Acorus, which is important for understanding the origin and evolution of monocots. Using the data from morphology, anatomy, and biogeography, we argue that the type material of A. tatarinowii does not match the interpretation of the species name as adopted in the current literature and herbarium collections (to a taxon of the A. gramineus group from Southeast Asia) but rather belongs to the A. calamus group. Moreover, the name A. macrospadiceus also cannot be used because it was invalidly published. Under a narrow species concept, other appropriate species names should be found or proposed for the plants currently named A. tatarinowii and A. macrospadiceus. However, we discourage the use of a narrow species concept in the A. gramineus group as insufficiently justified and suggest recognizing a single polymorphic species, A. gramineus s.l., at least until a comprehensive taxonomic revision of the group is available. Apart from the presentation of our revised taxonomic framework, we update the geographical distributions of Acorus species in Vietnam, Laos, and Thailand

On generic rank and phylogenetic relationships of Dorycnopsis Boiss. (Leguminosae, Loteae)

Nuclear ribosomal ITS sequence data as well as morphological data show that Dorycnopsis gerardii (L.) Boiss. can not be placed in the genus Anthyllis L. The genus Dorycnopsis Boiss. includes two species, D. gerardii and D. abyssinica (A. Rich.) V.N. Tikhom. et D.D. Sokoloff (=Vermifrux abyssinica (A. Rich.) J.B. Gillett). Morphological similarity between Dorycnopsis gerardii and Anthyllis onobrychioides Cav. might be best explained by evolutionary parallelism. Anthyllis (including Hymenocarpos Savi but excluding Dorycnopsis and the monotypic Tripodion Medik.) is well-resolved as a highly supported monophyletic group in analyses of nrITS data set.Datos sobre la secuencia de ITS ribosómico nuclear así como datos morfológicos revelan que Dorycnopsis gerardii (L.) Boiss. no puede pertenecer al género Anthyllis L. El género Dorycnopsis Boiss. incluye dos especies, D. gerardii y D. abyssinica (A. Rich.) V.N. Tikhom. et D.D. Sokoloff (=Vermifrux abyssinica (A. Rich.) J.B. Gillett). La similitud morfológica entre Dorycnopsis gerardii y Anthyllis onobrychioides Cav. encuentra su explicación en un paralelismo evolutivo. Anthyllis (incluyendo a Hymenocarpos Savi, pero excluyendo a Dorycnopsis y al monotípico Tripodion Medik.) se considera, a partir del análisis del nrITS, un grupo monofílitico con un buen apoyo estadístico

On generic rank and phylogenetic relationships of Dorycnopsis Boiss. (Leguminosae, Loteae)

Nuclear ribosomal ITS sequence data as well as morphological data show that Dorycnopsis gerardii (L.) Boiss. can not be placed in the genus Anthyllis L. The genus Dorycnopsis Boiss. includes two species, D. gerardii and D. abyssinica (A. Rich.) V.N. Tikhom. et D.D. Sokoloff (=Vermifrux abyssinica (A. Rich.) J.B. Gillett). Morphological similarity between Dorycnopsis gerardii and Anthyllis onobrychioides Cav. might be best explained by evolutionary parallelism. Anthyllis (including Hymenocarpos Savi but excluding Dorycnopsis and the monotypic Tripodion Medik.) is well-resolved as a highly supported monophyletic group in analyses of nrITS data set.Datos sobre la secuencia de ITS ribosómico nuclear así como datos morfológicos revelan que Dorycnopsis gerardii (L.) Boiss. no puede pertenecer al género Anthyllis L. El género Dorycnopsis Boiss. incluye dos especies, D. gerardii y D. abyssinica (A. Rich.) V.N. Tikhom. et D.D. Sokoloff (=Vermifrux abyssinica (A. Rich.) J.B. Gillett). La similitud morfológica entre Dorycnopsis gerardii y Anthyllis onobrychioides Cav. encuentra su explicación en un paralelismo evolutivo. Anthyllis (incluyendo a Hymenocarpos Savi, pero excluyendo a Dorycnopsis y al monotípico Tripodion Medik.) se considera, a partir del análisis del nrITS, un grupo monofílitico con un buen apoyo estadístico