6,702 research outputs found
A three dimensional model of the Venusian thermosphere with superrotation
An improved three dimensional spectral model of the thermosphere of Venus is described. The model solves the Navier-Stokes equations and includes nonlinear effects for an arbitrary number of atmospheric species. A two dimensional axisymmetric model of the superrotation of the thermosphere is also presented. This model addresses the Pioneer-Venus mission finding, which suggested the thermospheric rotation rate to be much higher than that of the planet as seen from the asymmetric distribution of hydrogen and helium. Both models include the effects of an anisotropic eddy diffusion that is consistent with atmospheric mixing length theory
eingesetzt wird. A. nutzt dazu die Boolesche Logik (Algebra) mit den Operatoren AND, OR und NOT. Die logischen Operatoren ergeben folgende Mengen: A AND B
N2- Drucker, die ein Verfahren zum schnellen und kostengünstigen Erstellen von dreidimensionalen physikalischen Modellen (Prototypen) nutzen. Sie verwenden Pulvermaterialien, die sich durch Einspritzen eines Bindemittels verfestigen. 3D-D. verarbeiten CAD-Daten und sind für das „rapid prototyping “ inzwischen für unter $ 5.000 zu erwerben
Amorphous thin film growth: theory compared with experiment
Experimental results on amorphous ZrAlCu thin film growth and the dynamics of
the surface morphology as predicted from a minimal nonlinear stochastic
deposition equation are analysed and compared. Key points of this study are (i)
an estimation procedure for coefficients entering into the growth equation and
(ii) a detailed analysis and interpretation of the time evolution of the
correlation length and the surface roughness. The results corroborate the
usefulness of the deposition equation as a tool for studying amorphous growth
processes.Comment: 7 pages including 5 figure
Untangling the Conceptual Isssues Raised in Reydon and Scholz’s Critique of Organizational Ecology and Darwinian Populations
Reydon and Scholz raise doubts about the Darwinian status of organizational ecology by arguing that Darwinian principles are not applicable to organizational populations. Although their critique of organizational ecology’s typological essentialism is correct, they go on to reject the Darwinian status of organizational populations. This paper claims that the distinction between replicators and interactors, raised in modern philosophy of biology but not discussed by Reydon and Scholz, points the way forward for organizational ecologists. It is possible to conceptualise evolving Darwinian populations providing the inheritance mechanism is appropriately specified. By this approach, adaptation and selection are no longer dichotomised, and the evolutionary significance of knowledge transmission is highlightedPeer reviewe
Phonon anomalies and charge dynamics in Fe_{1-x}Cu_{x}Cr_{2}S_{4} single crystals
A detailed investigation of phonon excitations and charge carrier dynamics in
single crystals of Fe_{1-x}Cu_{x}Cr_{2}S_{4} (x = 0, 0.2, 0.4, 0.5) has been
performed by using infrared spectroscopy. In FeCr_{2}S_{4} the phonon
eigenmodes are strongly affected by the onset of magnetic order. Despite
enhanced screening effects, a continuous evolution of the phonon excitations
can be observed in the doped compounds with x = 0.2 (metallic) and x = 0.4, 0.5
(bad metals), but the effect of magnetic ordering on the phonons is strongly
reduced compared to x = 0. The Drude-like charge-carrier contribution to the
optical conductivity in the doped samples indicates that the colossal
magneto-resistance effect results from the suppression of spin-disorder
scattering.Comment: 8 pages, 6 figure
The effect of Wilson line moduli on CP-violation by soft supersymmetry breaking terms
The CP-violating phases in the soft supersymmetry-breaking sector in orbifold
compactifications with a continuous Wilson line are investigated. In this case
the modular symmetry is the Siegel modular group of genus two. In
particular, we study the case that the hidden sector non-perturbative
superpotential is determined by the Igusa cusp form of modular
weight 12. The effect of large non-perturbative corrections to the dilaton
K\"ahler potential on the resulting CP-violating phases is also investigated.Comment: LaTeX file, 12 pages plus 7 figures, to appear in Phys.Lett.
Mirror Symmetry and Landau Ginzburg Calabi-Yau Superpotentials in F-theory Compactifications
We study Landau Ginzburg (LG) theories mirror to 2D N=2 gauged linear sigma
models on toric Calabi-Yau manifolds. We derive and solve new constraint
equations for Landau Ginzburg elliptic Calabi-Yau superpotentials, depending on
the physical data of dual linear sigma models. In Calabi-Yau threefolds case,
we consider two examples. First, we give the mirror symmetry of the canonical
line bundle over the Hirzebruch surfaces . Second, we find a special
geometry with the affine so(8) Lie algebra toric data extending the geometry of
elliptically fibered K3. This geometry leads to a pure N=1 six dimensional
SO(8) gauge model from the F-theory compactification. For Calabi-Yau fourfolds,
we give a new algebraic realization for ADE hypersurfaces.Comment: 27 pages, latex. To appear in Journal of Physics A: Mathematical and
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