Algebraic theory of affine curvature tensors

We use curvature decompositions to construct generating sets for the space of algebraic curvature tensors and for the space of tensors with the same symmetries as those of a torsion free, Ricci symmetric connection; the latter naturally appear in relative hypersurface theory.Comment: The paper is dedicated to the memory of the first author (N. Blazic) who passed away Monday 10 October 200

Statistics of Lead Changes in Popularity-Driven Systems

We study statistical properties of the highest degree, or most popular, nodes in growing networks. We show that the number of lead changes increases logarithmically with network size N, independent of the details of the growth mechanism. The probability that the first node retains the lead approaches a finite constant for popularity-driven growth, and decays as N^{-phi}(ln N)^{-1/2}, with phi=0.08607..., for growth with no popularity bias.Comment: 4 pages, 4 figures, 2 column revtex format. Minor changes in response to referee comments. For publication in PR

On the Containment Problem for Linear Sets

It is well known that the containment problem (as well as the equivalence problem) for semilinear sets is log-complete at the second level of the polynomial hierarchy (where hardness even holds in dimension 1). It had been shown quite recently that already the containment problem for multi-dimensional linear sets is log-complete at the same level of the hierarchy (where hardness even holds when numbers are encoded in unary). In this paper, we show that already the containment problem for 1-dimensional linear sets (with binary encoding of the numerical input parameters) is log-hard (and therefore also log-complete) at this level. However, combining both restrictions (dimension 1 and unary encoding), the problem becomes solvable in polynomial time

Capillary rise dynamics of liquid hydrocarbons in mesoporous silica as explored by gravimetry, optical and neutron imaging: Nano-rheology and determination of pore size distributions from the shape of imbibition fronts

We present gravimetrical, optical, and neutron imaging measurements of the capillarity-driven infiltration of mesoporous silica glass by hydrocarbons. Square-root-of-time Lucas-Washburn invasion kinetics are found for linear alkanes from n-decane (C10) to n-hexacontane (C60) and for squalane, a branched alkane, in porous Vycor with 6.5 nm or 10 nm pore diameter, respectively. Humidity-dependent experiments allow us to study the influence on the imbibition kinetics of water layers adsorbed on the pore walls. Except for the longest molecule studied, C60, the invasion kinetics can be described by bulk fluidity and bulk capillarity, provided we assume a sticking, pore-wall adsorbed boundary layer, i.e. a monolayer of water covered by a monolayer of flat-laying hydrocarbons. For C60, however, an enhanced imbibition speed compared to the value expected in the bulk is found. This suggests the onset of velocity slippage at the silica walls or a reduced shear viscosity due to the transition towards a polymer-like flow in confined geometries. Both, light scattering and neutron imaging indicate a pronounced roughening of the imbibition fronts. Their overall shape and width can be resolved by neutron imaging. The fronts can be described by a superposition of independent wetting fronts moving with pore size-dependent square-root-of-time laws and weighted according to the pore size distributions obtained from nitrogen gas sorption isotherms. This finding indicates that the shape of the imbibition front in a porous medium, such as Vycor glass, with interconnected, elongated pores, is solely determined by independent movements of liquid menisci. These are dictated by the Laplace pressure and hydraulic permeability variations and thus the pore size variation at the invasion front. Our results suggest that pore size distributions can be derived from the broadening of imbibition fronts.Comment: 28 pages, 12 figures, pre-print, in pres

Anti-Interleukin-5-Therapie bei eosinophilen Erkrankungen

Zusammenfassung: Bei einer Reihe von Erkrankungen, die durch eine Eosinophilie charakterisiert sind, findet man erhöhte Spiegel von Interleukin- (IL-)5 im Blut und/oder Gewebe. IL-5 spielt eine wichtige Rolle in der Regulierung von Produktion, Differenzierung, Rekrutierung, Aktivierung und Überleben eosinophiler Granulozyten. Daher stellt die Neutralisation von IL-5 durch blockierende Antikörper einen vielversprechenden neuen Ansatz in der Therapie dieser Erkrankungen dar. Erste klinische Studien zeigten, dass es nach Applikation von Anti-IL-5-Antikörpern zu einem raschen Abfall der Eosinophilenzahlen im peripheren Blut kommt. Eine Abnahme der Beschwerden wurde bei der lymphozytären Form hypereosinophiler Syndrome, bei eosinophiler Ösophagitis und bei chronischer Rhinitis mit nasaler Polyposis beobachtet. Im Gegensatz dazu zeigte eine Anti-IL-5-Antikörper-Behandlung von Patienten mit Asthma bronchiale oder mit atopischem Ekzem nicht den erwarteten klinischen Effekt. Zukünftige Studien werden zeigen, bei welchen eosinophilen Erkrankungen eine Anti-IL-5-Therapie wirksam ist und welche Patientengruppen auf diese Therapie anspreche

Effects of Cutting Dates in Primary Growth, Water Soluble Carbohydrate Content and Nitrogen Fertilization on Regrowth of Perennial Ryegrass

In a field experiment, an early• and a late-maturing cultivar of perennial ryegrass were cut during the primary growth in 6-weekly intervals starting when the early cultivar (Lolium perenne L.) reached stage of growth 31 (Simon & Park 1983, Proceedings XIV IGC), at 2 levels of nitrogen fertilisation. Dry mailer yield (DMY) in the regrowth was determined 4 weeks after defoliation in the primary growth. DMY in the regrowth decreased with delayed cutting in the primary growth. No significant correlation existed between the content of water soluble carbohydrates (WSC) in 1he stubble at the time of defoliation in the primary growth, nnd regrowth. Differences in the regrowlh DMY could be attributed primarily to differences in the number of fertile tillers. The late-maturing cultivar achieved higher regrowth DMY and responded more favourably to increased nitrogen fertilisation than the early-maturing cultivar