Meandering periods and asymmetries in light curves of Miras: Observational evidence for low mass-loss rates

Some Miras -- long-period variables in late evolutionary stages -- have meandering pulsation periods and light curve asymmetries, the causes of which are still unclear. We aim to understand better the origin of these phenomena by investigating a sample of solar-neighbourhood Miras. We characterised this group of stars and related their variability characteristics to other stellar parameters. We analysed observations from several databases to obtain light curves with maximum time span and temporal coverage for a sample of 548 Miras. We determined their pulsation period evolution over a time span of many decades, searched for changes in the periods, and determined the amplitude of the period change. We also analysed the Fourier spectra with respect to possible secondary frequency maxima. The sample was divided into two groups with respect to the presence of light curve bumps. IR colours and indicators of the third dredge-up were collected to study the sample stars' mass-loss and deep mixing properties. Our analysis revealed one new star, T~Lyn, with a continuously changing period. The group of Miras with meandering period changes is exclusively made up of M-type stars. The Fourier spectra of the meandering period Miras have no prominent additional peaks, suggesting that additional pulsation modes are not the cause of the meandering periods. We confirm that bumps are more common among S and C Miras and show, for the first time, that Miras with bumps have lower mass-loss rates than those with regular, symmetric light curves. Also Miras with meandering period changes have relatively little mass loss. We conclude that Miras with strongly changing periods or asymmetries in their light curves have relatively low dust mass-loss rates. Meandering period changes and light curve asymmetries could be connected to He-shell flashes and third dredge-up episodes.Comment: 13 pages (plus 13 pages Appendix), 14 Figures, accepted for publication in A&

Effects of Dry Matter Content and Microbial Additive on Tifton 85 \u3ci\u3e(Cynodon dactylon ssp.)\u3c/i\u3e Wilted Silage Fermentation Parameters

The objective of this study was to evaluate the wilting and the addition of a bacterial-enzymatic additive effects on the fermentation parameters of Tifton 85 (Cynodon dactylon spp.) silage. Forage was stored as 326 kg bales wrapped with a plastic film. Treatments consisted of 5 forage dry matter levels (20-30%, 30-40%, 40-50%, 50 -60% e 60 a 70%) without additive and 3 dry matter levels (20-30%, 40-50%, e 60-70%) with additive. Buffered propionic acid solution was sprayed onto 60-70% dry matter bales, prior to wrapping, determining an additional treatment. Core samples were taken at 0, 6, 12 hours and 1, 2, 4, 8, 16, and 32 days after wrapping to establish silage pH and temperature trends. Field dry matter losses during the baling process were also evaluated. Bale weight with no additive decreased (364 kg to 254 kg) with increased forage DM content, which in turn resulted in lower bale bulk density (310 to 216 kg/m3 ). Lower field DM losses (281 to 177 kg/ha) were associated with higher forage DM content. Final silage pH and temperature peaks were increased at higher DM content, whereas the presence of microbial additive prevented temperature surge

Environmental Enhancement of DM Haloes

We study the properties of dark matter haloes of a LCDM model in different environments. Using the distance of the 5th nearest neighbour as an environmental density indicator, we show that haloes in a high density environment are more massive, richer, have larger radii and larger velocity dispersions than haloes in a low density environment. Haloes in high density regions move with larger velocities, and are more spherical than haloes in low density regions. In addition, low mass haloes in the vicinity of the most massive haloes are themselves more massive, larger, and have larger rms velocities and larger 3D velocities than low mass haloes far from massive haloes. The velocities of low mass haloes near massive haloes increase with the parent halo mass. Our results are in agreement with recent findings about environmental effects for groups and clusters of galaxies from deep (SDSS and LCRS) surveys.Comment: 9 pages, 7 figures, submitted for Astronomy and Astrophysic

Isolation and characterization of microsatellite markers in the portunid crab Liocarcinus depurator using FIASCO and 454 next-generation sequencing

The portunid crab Liocarcinus depurator is the dominant decapod crustacean present on mud bottoms of the continental shelf of the Mediterranean Sea. In order to better describe its genetic structure, a total of 11 microsatellites were isolated and tested in 28 L. depurator individuals from the Mediterranean locality of Tarragona. Initially, microsatellite isolation was carried out using the FIASCO methodology, but only 2 useful primer pairs could be designed. Given the low yield obtained, an alternative method based on 454 next-generation sequencing was assayed, which provided excellent results and from which another 9 primer pairs gave positive genotyping. All loci tested were polymorphic, and 2 to 24 (mean 10.54) alleles per locus were identified. The observed and expected heterozygosities per locus ranged from 0.214 to 0.926 and from 0.232 to 0.962, respectively. One locus (Ldep10) showed the presence of null alleles according to the Brookfield estimator implemented in MICROCHECKER. Nevertheless, none of the markers deviated significantly from Hardy–Weinberg equilibrium or showed evidence of linkage disequilibrium. This set of 11 markers is being used to study the population structure and genetic diversity of Liocarcinus depurator populations from both Mediterranean and adjacent Atlantic waters.The portunid crab Liocarcinus depurator is the dominant decapod crustacean present on mud bottoms of the continental shelf of the Mediterranean Sea. In order to better describe its genetic structure, a total of 11 microsatellites were isolated and tested in 28 L. depurator individuals from the Mediterranean locality of Tarragona. Initially, microsatellite isolation was carried out using the FIASCO methodology, but only 2 useful primer pairs could be designed. Given the low yield obtained, an alternative method based on 454 next-generation sequencing was assayed, which provided excellent results and from which another 9 primer pairs gave positive genotyping. All loci tested were polymorphic, and 2 to 24 (mean 10.54) alleles per locus were identified. The observed and expected heterozygosities per locus ranged from 0.214 to 0.926 and from 0.232 to 0.962, respectively. One locus (Ldep10) showed the presence of null alleles according to the Brookfield estimator implemented in MICROCHECKER. Nevertheless, none of the markers deviated significantly from Hardy–Weinberg equilibrium or showed evidence of linkage disequilibrium. This set of 11 markers is being used to study the population structure and genetic diversity of Liocarcinus depurator populations from both Mediterranean and adjacent Atlantic waters

Ellipsoidal configurations in the de Sitter spacetime

The cosmological constant $\Lambda$ modifies certain properties of large astrophysical rotating configurations with ellipsoidal geometries, provided the objects are not too compact. Assuming an equilibrium configuration and so using the tensor virial equation with $\Lambda$ we explore several equilibrium properties of homogeneous rotating ellipsoids. One shows that the bifurcation point, which in the oblate case distinguishes the Maclaurin ellipsoid from the Jacobi ellipsoid, is sensitive to the cosmological constant. Adding to that, the cosmological constant allows triaxial configurations of equilibrium rotating the minor axis as solutions of the virial equations. The significance of the result lies in the fact that minor axis rotation is indeed found in nature. Being impossible for the oblate case, it is permissible for prolate geometries, with $\Lambda$ zero and positive. For the triaxial case, however, an equilibrium solution is found only for non-zero positive $\Lambda$. Finally, we solve the tensor virial equation for the angular velocity and display special effects of the cosmological constant there.Comment: 15 pages, 11 figures, published in Class. Quant. Grav. References adde

Cluster-Galaxy Correlations in CDM Models

We study the ability of COBE-normalized CDM models to reproduce observed properties of the distribution of galaxies and clusters using N-body numerical simulations. We analyze the galaxy-galaxy and cluster-galaxy two-point correlation functions, $\xi_{gg}$ and $\xi_{cg}$, in open ($\Omega_{0}=0.4, \Omega_{\Lambda}=0, \sigma_8=0.75$), and flat ($\Omega_{0}=0.3, \Omega_{\Lambda}=0.7, \sigma_8=1.05$) CDM models which both reproduce the observed abundances of rich clusters of galaxies. To compare models with observations we compute projected cross-correlation functions $\omega_{gg}$ and $\omega_{cg}$ to derive the corresponding $\xi_{gg}$ and $\xi_{cg}$. We use target galaxies selected from Las Campanas Redshift Survey, target clusters selected from the APM Cluster Survey and tracer galaxies from the Edinburgh Durham Sky Survey catalog.Comment: 13 pages, 6 figures, to appear in: The Astrophysical Journa

In-situ formation of solidified hydrogen thin-membrane targets using a pulse tube cryocooler

An account is given of the Central Laser Facility's work to produce a cryogenic hydrogen targetry system using a pulse tube cryocooler. Due to the increasing demand for low Z thin laser targets, CLF (in collaboration with TUD) have been developing a system which allows the production of solid hydrogen membranes by engineering a design which can achieve this remotely; enabling the gas injection, condensation and solidification of hydrogen without compromising the vacuum of the target chamber. A dynamic sealing mechanism was integrated which allows targets to be grown and then remotely exposed to open vacuum for laser interaction. Further research was conducted on the survivability of the cryogenic targets which concluded that a warm gas effect causes temperature spiking when exposing the solidified hydrogen to the outer vacuum. This effect was shown to be mitigated by improving the pumping capacity of the environment and reducing the minimum temperature obtainable on the target mount. This was achieved by developing a two-stage radiation shield encased with superinsulating blanketing; reducing the base temperature from 14 0.5 K to 7.2 0.2 K about the coldhead as well as improving temperature control stability following the installation of a high-performance temperature controller and sensor apparatus. The system was delivered experimentally and in July 2014 the first laser shots were taken upon hydrogen targets in the Vulcan TAP facility.</p