Cosmological spacetimes balanced by a scale covariant scalar field

A scale invariant, Weyl geometric, Lagrangian approach to cosmology is explored, with a a scalar field phi of (scale) weight -1 as a crucial ingredient besides classical matter \cite{Tann:Diss,Drechsler:Higgs}. For a particularly simple class of Weyl geometric models (called {\em Einstein-Weyl universes}) the Klein-Gordon equation for phi is explicitly solvable. In this case the energy-stress tensor of the scalar field consists of a vacuum-like term Lambda g_{mu nu} with variable coefficient Lambda, depending on matter density and spacetime geometry, and of a dark matter like term. Under certain assumptions on parameter constellations, the energy-stress tensor of the phi-field keeps Einstein-Weyl universes in locally stable equilibrium. A short glance at observational data, in particular supernovae Ia (Riess ea 2007), shows interesting empirical properties of these models.Comment: 28 pages, 1 figure, accepted by Foundations of Physic

Germinal Centers without T Cells

Germinal centers are critical for affinity maturation of antibody (Ab) responses. This process allows the production of high-efficiency neutralizing Ab that protects against virus infection and bacterial exotoxins. In germinal centers, responding B cells selectively mutate the genes that encode their receptors for antigen. This process can change Ab affinity and specificity. The mutated cells that produce high-affinity Ab are selected to become Ab-forming or memory B cells, whereas cells that have lost affinity or acquired autoreactivity are eliminated. Normally, T cells are critical for germinal center formation and subsequent B cell selection. Both processes involve engagement of CD40 on B cells by T cells. This report describes how high-affinity B cells can be induced to form large germinal centers in response to (4-hydroxy-3-nitrophenyl) acetyl (NP)-Ficoll in the absence of T cells or signaling through CD40 or CD28. This requires extensive cross-linking of the B cell receptors, and a frequency of antigen-specific B cells of at least 1 in 1,000. These germinal centers abort dramatically at the time when mutated high-affinity B cells are normally selected by T cells. Thus, there is a fail-safe mechanism against autoreactivity, even in the event of thymus-independent germinal center formation

Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set

We report a measurement of the bottom-strange meson mixing phase \beta_s using the time evolution of B0_s -> J/\psi (->\mu+\mu-) \phi (-> K+ K-) decays in which the quark-flavor content of the bottom-strange meson is identified at production. This measurement uses the full data set of proton-antiproton collisions at sqrt(s)= 1.96 TeV collected by the Collider Detector experiment at the Fermilab Tevatron, corresponding to 9.6 fb-1 of integrated luminosity. We report confidence regions in the two-dimensional space of \beta_s and the B0_s decay-width difference \Delta\Gamma_s, and measure \beta_s in [-\pi/2, -1.51] U [-0.06, 0.30] U [1.26, \pi/2] at the 68% confidence level, in agreement with the standard model expectation. Assuming the standard model value of \beta_s, we also determine \Delta\Gamma_s = 0.068 +- 0.026 (stat) +- 0.009 (syst) ps-1 and the mean B0_s lifetime, \tau_s = 1.528 +- 0.019 (stat) +- 0.009 (syst) ps, which are consistent and competitive with determinations by other experiments.Comment: 8 pages, 2 figures, Phys. Rev. Lett 109, 171802 (2012

Cosmological observations in non-local F(R)F(R) cosmology

In this article in a generalization of our previous work, we investigate the dynamics of the non-local $F(R)$ gravity after casting it into local form. The non-singular bouncing behavior and quintom model of dark energy are achieved without involving negative kinetic energy fields. Two cosmological tests are performed to constrain the model parameters. In case of phantom crossing the distance modulus predicted by the model best-fits the observational data. In comparison with the CPL parametrization for drift velocity, the model in some redshift intervals is in good agreement with the data.Comment: 12 pages, 7 figures, will be published in Astrophysics and space scienc

Molecular data confirm the position of Flakea papillata in the Verrucariaceae

5Flakea papillata is a predominantly tropical, widespread lichen characterized by flake-like thalli of narrowly arranged, irregularly wrinkled, small bluish-green lobes, whose taxonomic position was unclear. The lichen shows superficial similarity with either algal colonies, bryophytes or fern prothallia, but the production of zeorin and other triterpenoids supports its inclusion in the ascomycetes. Analysis of the nuclear large and small subunits rRNA sequence data of samples from different origins supports the position of F. papillata within the Verrucariaceae: it forms its own supported clade not related to the core of Agonimia, in which it has been previously placed.nonemixedL. Muggia; C. Gueidan; G.B. Perlmutter; O.E. Eriksson; M. GrubeMuggia, Lucia; C., Gueidan; G. B., Perlmutter; O. E., Eriksson; M., Grub

Molecular data confirm the position of Flakea papillata in the Verrucariaceae

Flakea papillata is a predominantly tropical, widespread lichen characterized by flake-like thalli of narrowly arranged, irregularly wrinkled, small bluish-green lobes, whose taxonomic position was unclear. The lichen shows superficial similarity with either algal colonies, bryophytes or fern prothallia, but the production of zeorin and other triterpenoids supports its inclusion in the ascomycetes. Analysis of the nuclear large and small subunits rRNA sequence data of samples from different origins supports the position of F. papillata within the Verrucariaceae: it forms its own supported clade not related to the core of Agonimia, in which it has been previously placed