290 research outputs found
Überlegungen zur Finanzierung der vorgezogenen Steuersenkung
In der öffentlichen Diskussion ist die Frage, wie das Vorziehen der für 2005 beschlossenen Steuersenkung auf 2004 zu finanzieren ist. Prof. Dr. Albert J. Rädler, München, entwickelt einige Ideen und Vorschläge zur Gegenfinanzierung.Steuersystem, Steuer, Steuerbegünstigung, Subvention, Grundsteuer, Deutschland
Neue Trends im europäischen und internationalen Steuerrecht
Prof. Dr. Albert J. Rädler gibt in seinem Vortrag, den er beim D-A-CH Steuer-Kongress am 28. März 2003 in Wien gehalten hat, einen Überblick über neue Trends des europäischen und internationalen Steuerrechts, die sich im Zuge der Europäisierung und Globalisierung abzeichnen. Insbesondere geht er auf die Auswirkungen der grenzüberschreitenden Marktöffnung auf die Körperschaft-, Einkommen- und Mehrwertsteuer ein, zeigt die Einwicklung des Doppelbesteuerungsabkommens auf und geht der Frage nach, welche Folgen es für die Wirtschaft hätte, würde die IAS-Bilanzierung für die Besteuerung maßgeblich.EU-Steuerrecht, Internationales Steuerrecht, Globalisierung, Körperschaftsteuer, Einkommensteuer, Umsatzsteuer, Doppelbesteuerung, Europäische Wirtschafts- und Währungsunion
Magnetoconvection and dynamo coefficients III: alpha-effect and magnetic pumping in the rapid rotation regime
Aims. The alpha- and gamma-effects, which are responsible for the generation
and turbulent pumping of large scale magnetic fields, respectively, due to
passive advection by convection are determined in the rapid rotation regime
corresponding to the deep layers of the solar convection zone.
Methods. A 3D rectangular local model is used for solving the full set of MHD
equations in order to compute the electromotive force (emf), E = ,
generated by the interaction of imposed weak gradient-free magnetic fields and
turbulent convection with varying rotational influence and latitude. By
expanding the emf in terms of the mean magnetic field, E_i = a_ij , all
nine components of a_ij are computed. The diagonal elements of a_ij describe
the alpha-effect, whereas the off-diagonals represent magnetic pumping. The
latter is essentially the advection of magnetic fields by means other than the
underlying large-scale velocity field. Comparisons are made to analytical
expressions of the coefficients derived under the first-order smoothing
approximation (FOSA).
Results. In the rapid rotation regime the latitudinal dependence of the
alpha-components responsible for the generation of the azimuthal and radial
fields does not exhibit a peak at the poles, as is the case for slow rotation,
but at a latitude of about 30 degrees. The magnetic pumping is predominantly
radially down- and latitudinally equatorward as in earlier studies. The
numerical results compare surprisingly well with analytical expressions derived
under first-order smoothing, although the present calculations are expected to
lie near the limits of the validity range of FOSA.Comment: 14 pages, 12 figures, accepted for publication in Astronomy &
Astrophysic
A phase of liposomes with entangled tubular vesicles
An equilibrium phase belonging to the family of bilayer liposomes in ternary mixtures of dimyristoylphosphatidylcholine (DMPC), water, and geraniol (a biological alcohol derived from oil-soluble vitamins that acts as a cosurfactant) has been identified. Electron and optical microscopy reveal the phase, labeled Ltv, to be composed of highly entangled tubular vesicles. In situ x-ray diffraction confirms that the tubule walls are multilamellar with the lipids in the chain-melted state. Macroscopic observations show that the Ltv phase coexists with the well-known L4 phase of spherical vesicles and a bulk L alpha phase. However, the defining characteristic of the Ltv phase is the Weissenberg rod climbing effect under shear, which results from its polymer-like entangled microstructure
Cellular self-organization on micro-structured surfaces
Micro-patterned surfaces are frequently used in high-throughput single-cell studies, as they allow one to image isolated cells in defined geometries. Commonly, cells are seeded in excess onto the entire chip, and non-adherent cells are removed from the unpatterned sectors by rinsing. Here, we report on the phenomenon of cellular self-organization, which allows for autonomous positioning of cells on micro-patterned surfaces over time. We prepared substrates with a regular lattice of protein-coated adhesion sites surrounded by PLL-g-PEG passivated areas, and studied the time course of cell ordering. After seeding, cells randomly migrate over the passivated surface until they find and permanently attach to adhesion sites. Efficient cellular self-organization was observed for three commonly used cell lines (HuH7, A549, and MDA-MB-436), with occupancy levels typically reaching 40-60% after 3-5 h. The time required for sorting was found to increase with increasing distance between adhesion sites, and is well described by the time-to-capture in a random-search model. Our approach thus paves the way for automated filling of cell arrays, enabling high-throughput single-cell analysis of cell samples without losses
Kinematic frames and "active longitudes": does the Sun have a face?
It has recently been claimed that analysis of Greenwich sunspot data over 120
years reveals that sunspot activity clusters around two longitudes separated by
180 degrees (``active longitudes'') with clearly defined differential rotation
during activity cycles.In the present work we extend this critical examination
of methodology to the actual Greenwich sunspot data and also consider newly
proposed methods of analysis claiming to confirm the original identification of
active longitudes. Our analysis revealed that values obtained for the
parameters of differential rotation are not stable across different methods of
analysis proposed to track persistent active longitudes. Also, despite a very
thorough search in parameter space, we were unable to reproduce results
claiming to reveal the century-persistent active longitudes. We can therefore
say that strong and well substantiated evidence for an essential and
century-scale persistent nonaxisymmetry in the sunspot distribution does not
exist.Comment: 14 pages, 1 table, 21 figures, accepted in A&
Alpha effect and turbulent diffusion from convection
(abridged) Aims: To study turbulent transport coefficients that describe the
evolution of large-scale magnetic fields in turbulent convection. Methods: We
use the test field method together with 3D numerical simulations of turbulent
convection with shear and rotation to compute turbulent transport coefficients
describing the evolution of large-scale magnetic fields in mean-field theory in
the kinematic regime. 1D mean-field models are used with the derived turbulent
transport coefficients to compare with direct simulations. Results: The
alpha-effect increases monotonically as rotation increases. Turbulent
diffusivity, eta_t, is proportional to the square of the turbulent vertical
velocity. Whereas eta_t decreases approximately inversely proportional to the
wavenumber of the field, the alpha-effect and turbulent pumping show a more
complex behaviour. In the presence of shear and no rotation a small
alpha-effect is induced which does not seem to show any consistent trend as a
function of shear. If the shear is large enough, this small alpha is able to
excite a dynamo in the mean-field model. The coefficient responsible for
driving the shear-current effect shows several sign changes as a function of
depth but is also able to contribute to dynamo action in the mean-field model.
The growth rates in these cases are well below those in direct simulations
suggesting that an incoherent alpha-shear dynamo may also act in them. If both
rotation and shear are present, the alpha-effect is more pronounced. The
combination of the shear-current and Omega x J-effects is also stronger than in
the case of shear only, but subdominant to the alpha-shear dynamo. The results
of direct simulations are consistent with mean-field models where all of these
effects are taken into account without the need to invoke incoherent effects.Comment: 14 pages, 14 figures, minor changes to match with the published
versio
Ring-Shaped Microlanes and Chemical Barriers as a Platform for Probing Single-Cell Migration
Quantification and discrimination of pharmaceutical and disease-related effects on cell migration requires detailed characterization of single-cell motility. In this context, micropatterned substrates that constrain cells within defined geometries facilitate quantitative readout of locomotion. Here, we study quasi-one-dimensional cell migration in ring-shaped microlanes. We observe bimodal behavior in form of alternating states of directional migration (run state) and reorientation (rest state). Both states show exponential lifetime distributions with characteristic persistence times, which, together with the cell velocity in the run state, provide a set of parameters that succinctly describe cell motion. By introducing PEGylated barriers of different widths into the lane, we extend this description by quantifying the effects of abrupt changes in substrate chemistry on migrating cells. The transit probability decreases exponentially as a function of barrier width, thus specifying a characteristic penetration depth of the leading lamellipodia. Applying this fingerprint-like characterization of cell motion, we compare different cell lines, and demonstrate that the cancer drug candidate salinomycin affects transit probability and resting time, but not run time or run velocity. Hence, the presented assay allows to assess multiple migration-related parameters, permits detailed characterization of cell motility, and has potential applications in cell biology and advanced drug screening
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