Vesicles in a Poiseuille flow

Vesicle dynamics in unbounded Poiseuille flow is analyzed using a small-deformation theory. Our analytical results quantitatively describe vesicle migration and provide new physical insights. At low ratio between the inner and outer viscosity $\lambda$ (i.e. in the tank-treading regime), the vesicle always migrates towards the flow centerline, unlike other soft particles such as drops. Above a critical $\lambda$, vesicle tumbles and cross-stream migration vanishes. A novel feature is predicted, namely the coexistence of two types of nonequilibrium configurations at the centreline, a bullet-like and a parachute-like shapes.Comment: 4 pages and 5 figure

Untersuchungen zu Fütterung, Milchleistung und Tiergesundheit von Milchkühen im Ökologischen Landbau

The breeding scheme entails yield differences of more than 2 000 kg energy corrected milk (ECM) per cow and year. On average, farms feeding less concentrate yielded slightly lower milk yields per cow and year, however, because of the longer productive life the cows showed similar milk yields over their lifetime. The farms investigated so far appeared to have healthy cows, even if fed low levels of concentrates or in the case of extremely low or high urea contents in the milk. These values could indicate the cows’ ability to compensate for short-dated changes

Kraftfuttergaben und Milchleistung bei Weidegang von Milchviehherden im ökologischen Landbau

During grazing, the efficiency of concentrate feeding on milk yields is low, especially when white clover is present in the sward (Wilkens et al., 1994). Clover in animal feed enhances forage intake; feeding trials have shown increased intake rates by 15-30 % (Paul, 2003). These results are of special interest for organic farms, where clover has a higher impact on the farming system. In the experimental organic farm of the Landwirtschaftskammer Nordrhein-Westfalen (Haus Riswick) the concentrate rate fed during grazing time showed no influence upon milk yields (2,6 resp.4,7 kg DM concentrate/ animal/day). In agreement with these results a three years investigation on 89 organic farms in Northwest Germany showed no effect of concentrate feeding on milk yield during the grazing season. Furthermore, a reduction or increase of concentrate rates during the grazing season did not show any differences in animal health so far

The integral monodromy of hyperelliptic and trielliptic curves

We compute the \integ/\ell and \integ_\ell monodromy of every irreducible component of the moduli spaces of hyperelliptic and trielliptic curves. In particular, we provide a proof that the \integ/\ell monodromy of the moduli space of hyperelliptic curves of genus $g$ is the symplectic group \sp_{2g}(\integ/\ell). We prove that the \integ/\ell monodromy of the moduli space of trielliptic curves with signature $(r,s)$ is the special unitary group \su_{(r,s)}(\integ/\ell\tensor\integ[\zeta_3])

A simplified particulate model for coarse-grained hemodynamics simulations

Human blood flow is a multi-scale problem: in first approximation, blood is a dense suspension of plasma and deformable red cells. Physiological vessel diameters range from about one to thousands of cell radii. Current computational models either involve a homogeneous fluid and cannot track particulate effects or describe a relatively small number of cells with high resolution, but are incapable to reach relevant time and length scales. Our approach is to simplify much further than existing particulate models. We combine well established methods from other areas of physics in order to find the essential ingredients for a minimalist description that still recovers hemorheology. These ingredients are a lattice Boltzmann method describing rigid particle suspensions to account for hydrodynamic long range interactions and---in order to describe the more complex short-range behavior of cells---anisotropic model potentials known from molecular dynamics simulations. Paying detailedness, we achieve an efficient and scalable implementation which is crucial for our ultimate goal: establishing a link between the collective behavior of millions of cells and the macroscopic properties of blood in realistic flow situations. In this paper we present our model and demonstrate its applicability to conditions typical for the microvasculature.Comment: 12 pages, 11 figure

The Migration of Elites in a Borderless World: Citizenship as an Incentive for Professionals and Managers?

Der Artikel geht der Frage nach, inwiefern die geöffneten Türen für die Immigration Hochqualifizierter in den OECD-Ländern tatsächlich zu einer verstärkten Migrationsbewegung führen. Die Analyse von Daten zu Eliten- und Hochqualifiziertenmigration in Ostasien, Europa und den USA führt zu dem Ergebnis, dass diese dem Muster einer „brain circulation“ folgt und die Staatsbürgerrechte dabei keine entscheidende Rolle spielen

A multiple scale model for tumor growth

We present a physiologically structured lattice model for vascular tumor growth which accounts for blood flow and structural adaptation of the vasculature, transport of oxygen, interaction between cancerous and normal tissue, cell division, apoptosis, vascular endothelial growth factor release, and the coupling between these processes. Simulations of the model are used to investigate the effects of nutrient heterogeneity, growth and invasion of cancerous tissue, and emergent growth laws