Cytological and molecular description of Hamiltosporidium tvaerminnensis gen. et sp. nov., a microsporidian parasite of Daphnia magna, and establishment of Hamiltosporidium magnivora comb. nov.

We describe the new microsporidium Hamiltosporidium tvaerminnensis gen. et sp. nov. with an emphasis on its ultrastructural characteristics and phylogenetic position as inferred from the sequence data of SSU rDNA, alpha-and beta-tubulin. This parasite was previously identified as Octosporea bayeri Jirovec, 1936 and has become a model system to study the ecology, epidemiology, evolution and genomics of microsporidia - host interactions. Here, we present evidence that shows its differences from O. bayeri. Hamiltosporidium tvaerminnensis exclusively infects the adipose tissue, the ovaries and the hypodermis of Daphnia magna and is found only in host populations located in coastal rock pool populations in Finland and Sweden. Merogonial stages of H. tvaerminnensis have isolated nuclei; merozoites are formed by binary fission or by the cleaving of a plasmodium with a small number of nuclei. A sporogonial plasmodium with isolated nuclei yields 8 sporoblasts. Elongated spores are generated by the most finger-like plasmodia. The mature spores are polymorphic in shape and size. Most spores are pyriform (4.9-5.6x2.2-2.3 mu m) and have their polar filament arranged in 12-13 coils. A second, elongated spore type (6.8-12.0x1.6-2.1 mu m) is rod-shaped with blunt ends and measures 6.8-12.0x1.6-2.1 mu m. The envelope of the sporophorous vesicle is thin and fragile, formed at the beginning of the sporogony. Cytological and molecular comparisons with Flabelliforma magnivora, a parasite infecting the same tissues in the same host species, reveal that these two species are very closely related, yet distinct. Moreover, both cytological and molecular data indicate that these species are quite distant from F. montana, the type species of the genus Flabelliforma. We therefore propose that F. magnivora also be placed in Hamiltosporidium gen. nov

Multiple scattering formalism for correlated systems: A KKR+DMFT approach

We present a charge and self-energy self-consistent computational scheme for correlated systems based on the Korringa-Kohn-Rostoker (KKR) multiple scattering theory with the many-body effects described by the means of dynamical mean field theory (DMFT). The corresponding local multi-orbital and energy dependent self-energy is included into the set of radial differential equations for the single-site wave functions. The KKR Green's function is written in terms of the multiple scattering path operator, the later one being evaluated using the single-site solution for the $t$-matrix that in turn is determined by the wave functions. An appealing feature of this approach is that it allows to consider local quantum and disorder fluctuations on the same footing. Within the Coherent Potential Approximation (CPA) the correlated atoms are placed into a combined effective medium determined by the dynamical mean field theory (DMFT) self-consistency condition. Results of corresponding calculations for pure Fe, Ni and Fe$_{x}$Ni$_{1-x}$ alloys are presented.Comment: 25 pages, 5 fig. acepted PR

Observation and theoretical description of the pure Fano-effect in the valence-band photo-emission of ferromagnets

The pure Fano-effect in angle-integrated valence-band photo-emission of ferromagnets has been observed for the first time. A contribution of the intrinsic spin polarization to the spin polarization of the photo-electrons has been avoided by an appropriate choice of the experimental parameters. The theoretical description of the resulting spectra reveals a complete analogy to the Fano-effect observed before for paramagnetic transition metals. While the theoretical photo-current and spin difference spectra are found in good quantitative agreement with experiment in the case of Fe and Co only a qualitative agreement could be achieved in the case of Ni by calculations on the basis of plain local spin density approximation (LSDA). Agreement with experimental data could be improved in this case in a very substantial way by a treatment of correlation effects on the basis of dynamical mean field theory (DMFT).Comment: 11 pages, 3 figures accepted by PR

Origin of facultative heterochromatin in the endosperm of Gagea lutea (Liliaceae)

Peer reviewedPostprin

The Universal Gaussian in Soliton Tails

We show that in a large class of equations, solitons formed from generic initial conditions do not have infinitely long exponential tails, but are truncated by a region of Gaussian decay. This phenomenon makes it possible to treat solitons as localized, individual objects. For the case of the KdV equation, we show how the Gaussian decay emerges in the inverse scattering formalism.Comment: 4 pages, 2 figures, revtex with eps

Cytological and molecular description of Hamiltosporidium tvaerminnensis gen. et sp. nov., a microsporidian parasite of Daphnia magna, and establishment of Hamiltosporidium magnivora comb. nov

We describe the new microsporidium Hamiltosporidium tvaerminnensis gen. et sp. nov. with an emphasis on its ultrastructural characteristics and phylogenetic position as inferred from the sequence data of SSU rDNA, alpha- and beta-tubulin. This parasite was previously identified as Octosporea bayeri Jírovec, 1936 and has become a model system to study the ecology, epidemiology, evolution and genomics of microsporidia - host interactions. Here, we present evidence that shows its differences from O. bayeri. Hamiltosporidium tvaerminnensis exclusively infects the adipose tissue, the ovaries and the hypodermis of Daphnia magna and is found only in host populations located in coastal rock pool populations in Finland and Sweden. Merogonial stages of H. tvaerminnensis have isolated nuclei; merozoites are formed by binary fission or by the cleaving of a plasmodium with a small number of nuclei. A sporogonial plasmodium with isolated nuclei yields 8 sporoblasts. Elongated spores are generated by the most finger-like plasmodia. The mature spores are polymorphic in shape and size. Most spores are pyriform (4·9-5·6×2·2-2·3 μm) and have their polar filament arranged in 12-13 coils. A second, elongated spore type (6·8-12·0×1·6-2·1 μm) is rod-shaped with blunt ends and measures 6·8-12·0×1·6-2·1 μm. The envelope of the sporophorous vesicle is thin and fragile, formed at the beginning of the sporogony. Cytological and molecular comparisons with Flabelliforma magnivora, a parasite infecting the same tissues in the same host species, reveal that these two species are very closely related, yet distinct. Moreover, both cytological and molecular data indicate that these species are quite distant from F. montana, the type species of the genus Flabelliforma. We therefore propose that F. magnivora also be placed in Hamiltosporidium gen. no

Orbital magnetism in transition-metal systems: The role of local correlation effects

The influence of correlation effects on the orbital moments for transition metals and their alloys is studied by first-principle relativistic Density Functional Theory in combination with the Dynamical Mean-Field Theory. In contrast to the previous studies based on the orbital polarization corrections we obtain an improved description of the orbital moments for wide range of studied systems as bulk Fe, Co and Ni, Fe-Co disordered alloys and 3$d$ impurities in Au. The proposed scheme can give simultaneously a correct dynamical description of the spectral function as well as static magnetic properties of correlated disordered metals.Comment: EPL accepte

About the strength of correlation effects in the electronic structure of iron

The strength of electronic correlation effects in the spin-dependent electronic structure of ferromagnetic bcc Fe(110) has been investigated by means of spin and angle-resolved photoemission spectroscopy. The experimental results are compared to theoretical calculations within the three-body scattering approximation and within the dynamical mean-field theory, together with one-step model calculations of the photoemission process. This comparison indicates that the present state of the art many-body calculations, although improving the description of correlation effects in Fe, give too small mass renormalizations and scattering rates thus demanding more refined many-body theories including non-local fluctuations.Comment: 4 pages, 4 figure

Electron correlations in Co2_2Mn1−x_{1-x}Fex_xSi Heusler compounds

This study presents the effect of local electronic correlations on the Heusler compounds Co$_2$Mn$_{1-x}$Fe$_x$Si as a function of the concentration $x$. The analysis has been performed by means of first-principles band-structure calculations based on the local approximation to spin-density functional theory (LSDA). Correlation effects are treated in terms of the Dynamical Mean-Field Theory (DMFT) and the LSDA+U approach. The formalism is implemented within the Korringa-Kohn-Rostoker (KKR) Green's function method. In good agreement with the available experimental data the magnetic and spectroscopic properties of the compound are explained in terms of strong electronic correlations. In addition the correlation effects have been analysed separately with respect to their static or dynamical origin. To achieve a quantitative description of the electronic structure of Co$_2$Mn$_{1-x}$Fe$_x$Si both static and dynamic correlations must be treated on equal footing.Comment: 12 pages, 5 figure