Astrophysical Configurations with Background Cosmology: Probing Dark Energy at Astrophysical Scales

We explore the effects of a positive cosmological constant on astrophysical and cosmological configurations described by a polytropic equation of state. We derive the conditions for equilibrium and stability of such configurations and consider some astrophysical examples where our analysis may be relevant. We show that in the presence of the cosmological constant the isothermal sphere is not a viable astrophysical model since the density in this model does not go asymptotically to zero. The cosmological constant implies that, for polytropic index smaller than five, the central density has to exceed a certain minimal value in terms of the vacuum density in order to guarantee the existence of a finite size object. We examine such configurations together with effects of $\Lambda$ in other exotic possibilities, such as neutrino and boson stars, and we compare our results to N-body simulations. The astrophysical properties and configurations found in this article are specific features resulting from the existence of a dark energy component. Hence, if found in nature would be an independent probe of a cosmological constant, complementary to other observations.Comment: 23 pages, 11 figures, 2 tables. Reference added. Mon. Not. Roy. Astro. Soc in prin

Mass-varying neutrino in light of cosmic microwave background and weak lensing

We aim to constrain mass-varying neutrino models using large scale structure observations and produce forecast for the Euclid survey. We investigate two models with different scalar field potential and both positive and negative coupling parameters \beta. These parameters correspond to growing or decreasing neutrino mass, respectively. We explore couplings up to |\beta|<5. In the case of the exponential potential, we find an upper limit on $\Omega_\nu h^2$<0.004 at 2-$\sigma$ level. In the case of the inverse power law potential the null coupling can be excluded with more than 2-\sigma significance; the limits on the coupling are \beta>3 for the growing neutrino mass and \beta<-1.5 for the decreasing mass case. This is a clear sign for a preference of higher couplings. When including a prior on the present neutrino mass the upper limit on the coupling becomes |\beta|<3 at 2-$\sigma$ level for the exponential potential. Finally, we present a Fisher forecast using the tomographic weak lensing from an Euclid-like experiment and we also consider the combination with the cosmic microwave background (CMB) temperature and polarisation spectra from a Planck-like mission. If considered alone, lensing data is more efficient in constraining $\Omega_\nu$ with respect to CMB data alone. There is, however, a strong degeneracy in the \beta-$\Omega_\nu h^2$ plane. When the two data sets are combined, the latter degeneracy remains, but the errors are reduced by a factor ~2 for both parameters.Comment: 5 pages, 6 figures. Now published in A&A 500, 657-665 (2009

Rearranging the centromere of the human Y chromosome with φC31 integrase

We have investigated the ability of the integrase from the Streptomyces φC31 ‘phage to either delete or invert 1 Mb of DNA around the centromere of the human Y chromosome in chicken DT40 hybrid somatic cells. Reciprocal and conservative site-specific recombination was observed in 54% of cells expressing the integrase. The sites failed to recombine in the remaining cells because the sites had been damaged. The sequences of the damaged sites indicated that the damage arose as a result of repair of recombination intermediates by host cell pathways. The liability of recombination intermediates to damage is consistent with what is known about the mechanism of serine recombinase reactions. The structures of the products of the chromosome rearrangements were consistent with the published sequence of the Y chromosome indicating that the assembly of the highly repeated region between the sites is accurate to a resolution of about 50 kb. Mini-chromosomes lacking a centromere were not recovered which also suggested that neo-centromere formation occurs infrequently in vertebrate somatic cells. No ectopic recombination was observed between a φC31 integrase attB site and the chicken genome

Land, cane and coconuts : papers on the rural economy of Fiji

The three papers contained in this volume are the outcome of research into various aspects of employment generation and income distribution in Fiji agriculture, undertaken in 1982 and 1983. The papers were originally prepared as Working Papers for the Fiji Employment and Development Mission, which submitted its final report to the Fiji Government in 1984. Revised versions are published together here in order to make available to a wider readership the result of the research

The diversity of Class II transposable elements in mammalian genomes has arisen from ancestral phylogenetic splits during ancient waves of proliferation through the genome

DNA transposons make up three percent of the human genome, roughly the same percentage as genes. However, due to their inactivity, they are often ignored in favour of the more abundant, active, retroelements. Despite this relative ignominy, there are a number of interesting questions to be asked of these transposon families. One particular question relates to the timing of proliferation and inactivation of elements in a family. Does an ongoing process of turnover occur, or is the process more akin to a life cycle for the family, with elements proliferating rapidly before deactivation at a later date? We answer this question by tracing back to the most recent common ancestor of each modern transposon family, using two different methods. The first method identifies the most recent common ancestor of the species in which a family of transposon fossils can still be found, which we assume will have existed soon after the true origin date of the transposon family. The second method uses molecular dating techniques to predict the age of the most recent common ancestor element from which all elements found in a modern genome are descended. Independent data from five pairs of species are used in the molecular dating analysis: Human- Chimpanzee, Human-Orangutan, Dog-Panda, Dog-Cat and Cow-Pig. Orthologous pairs of elements from host species pairs are included, and the divergence dates of these species are used to constrain the analysis. We discover that, in general, the times to element common ancestry, for a given family, are the same for the different species pairs, suggesting that there has been no order-specific process of turnover. Furthermore, for most families, the ages of the common ancestor of the host species and of that of the elements are similar, suggesting a life cycle model for the proliferation of transposons. Where these two ages differ, in families found only in Primates and Rodentia, for example, we find that the host species date is later than that of the common ancestor of the elements, implying that there may be large deletions of elements from host species, examples of which were found in their ancestors

Cosmology with massive neutrinos coupled to dark energy

Cosmological consequences of a coupling between massive neutrinos and dark energy are investigated. In such models, the neutrino mass is a function of a scalar field, which plays the role of dark energy. The evolution of the background and cosmological perturbations are discussed. We find that mass-varying neutrinos can leave a significant imprint on the anisotropies in the cosmic microwave background and even lead to a reduction of power on large angular scales

LIM kinase inhibitors disrupt mitotic microtubule organization and impair tumor cell proliferation

The actin and microtubule cytoskeletons are critically important for cancer cell proliferation, and drugs that target microtubules are widely-used cancer therapies. However, their utility is compromised by toxicities due to dose and exposure. To overcome these issues, we characterized how inhibition of the actin and microtubule cytoskeleton regulatory LIM kinases could be used in drug combinations to increase efficacy. A previously-described LIMK inhibitor (LIMKi) induced dose-dependent microtubule alterations that resulted in significant mitotic defects, and increased the cytotoxic potency of microtubule polymerization inhibitors. By combining LIMKi with 366 compounds from the GSK Published Kinase Inhibitor Set, effective combinations were identified with kinase inhibitors including EGFR, p38 and Raf. These findings encouraged a drug discovery effort that led to development of CRT0105446 and CRT0105950, which potently block LIMK1 and LIMK2 activity in vitro, and inhibit cofilin phosphorylation and increase αTubulin acetylation in cells. CRT0105446 and CRT0105950 were screened against 656 cancer cell lines, and rhabdomyosarcoma, neuroblastoma and kidney cancer cells were identified as significantly sensitive to both LIMK inhibitors. These large-scale screens have identified effective LIMK inhibitor drug combinations and sensitive cancer types. In addition, the LIMK inhibitory compounds CRT0105446 and CRT0105950 will enable further development of LIMK-targeted cancer therapy