Density Dependence of the Mass Function of Globular Star Clusters in the Sombrero Galaxy and its Dynamical Implications

We have constructed the mass function of globular star clusters in the Sombrero galaxy in bins of different internal half-mass density rho_h and projected galactocentric distance R. This is based on the published measurements of the magnitudes and effective radii of the clusters by Spitler et al. (2006) in BVR images taken with the ACS on HST. We find that the peak of the mass function M_p increases with rho_h by a factor of about 4 but remains nearly constant with R. Our results are almost identical to those presented recently by McLaughlin & Fall (2007) for globular clusters in the Milky Way. The mass functions in both galaxies agree with a simple, approximate model in which the clusters form with a Schechter initial mass function and evolve subsequently by stellar escape driven by internal two-body relaxation. These findings therefore undermine recent claims that the present peak of the mass function of globular clusters must have been built into the initial conditions.Comment: Astrophysical Journal Letters, in press. 4 page

Complex Networks on a Rock Joint

A complex network approach on a rough fracture is developed. In this manner, some hidden metric spaces (similarity measurements) between apertures profiles are set up and a general evolutionary network in two directions (in parallel and perpendicular to the shear direction) is constructed. Also, an algorithm (COmplex Networks on Apertures: CONA) is proposed in which evolving of a network is accomplished using preferential detachments and attachments of edges (based on a competition and game manner) while the number of nodes is fixed. Also, evolving of clustering coefficients and number of edges display similar patterns as well as are appeared in shear stress, hydraulic conductivity and dilation changes, which can be engaged to estimate shear strength distribution of asperities.Comment: ROCKENG09: Proceedings of the 3rd CANUS Rock Mechanics Symposium, Toronto, May 2009 (Ed: M.Diederichs and G. Grasselli

PEST BIRDS AND MODERN ARCHITECTURE

We are offering some remarks on what the entomologist would call the areas of cultural control. Our interest in this approach developed out of a series of information discussions we\u27ve had concerning regional planning pro-grams at Penn State. Our ideas on the applications of this to bird management are not well developed; we\u27d be happy to hear your suggestions and comments. The ideas of cultural control are not new and are only one of many approaches. But perhaps we are reaching a stage of public concern about bird problems and about environmental contamination which make the climate for long range plan-ning and cooperation more favorable. Most of the investigators and PCOs engaged in the management of bird populations are aware that the problem has two basic approaches: attacking the birds directly or making the environment unsuitable. Both these approaches are generally applied after the bird problem has developed. In the terminology of the medical profession, we are treating symptoms. We build our cities, shopping centers, and airports and wait for the bird populations to develop. Then we use our ingenuity to attempt to remove the birds with poisons, repellents, or structural modifications, while at the same time, someone has to clean up the mess and mollify irritated citizens and customers. In this report, we shall suggest some of the ways of reducing bird problems at the design level—a method that can be considered ecological exclusion or preventive pest control

Relation and interactions among reading fluency and competence for adult education learners

This is the peer reviewed version of the following article: Mellard, D. F., Fall, E. E. and Woods, K. L. (2013), Relation and Interactions Among Reading Fluency and Competence for Adult Education Learners. Learning Disabilities Research & Practice, 28: 70–80. doi:10.1111/ldrp.12008, which has been published in final form at http://doi.org/10.1111/ldrp.12008. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.Statistical analyses of data from an academically diverse sample of 276 adult basic and secondary education learners extends understanding of the relation of and interactions between oral reading fluency and reading competence indices. Significant interactions between total word rate and word error rate that differed in relation to two measures of reading competence suggest that adult literacy instructors should emphasize fluency instruction to a greater or lesser degree depending on whether the major goal of instruction is academic reading (e.g., being able to comprehend a textbook) or functional reading (e.g., being able to fill out a job application)

Modeling the dynamical evolution of the M87 globular cluster system

We study the dynamical evolution of the M87 globular cluster system (GCS) with a number of numerical simulations. We explore a range of different initial conditions for the GCS mass function (GCMF), for the GCS spatial distribution and for the GCS velocity distribution. We confirm that an initial power-law GCMF like that observed in young cluster systems can be readily transformed through dynamical processes into a bell-shaped GCMF. However,only models with initial velocity distributions characterized by a strong radial anisotropy increasing with the galactocentric distance are able to reproduce the observed constancy of the GCMF at all radii.We show that such strongly radial orbital distributions are inconsistent with the observed kinematics of the M87 GCS. The evolution of models with a bell-shaped GCMF with a turnover similar to that currently observed in old GCS is also investigated. We show that models with this initial GCMF can satisfy all the observational constraints currently available on the GCS spatial distribution,the GCS velocity distribution and on the GCMF properties.In particular these models successfully reproduce both the lack of a radial gradient of the GCS mean mass recently found in an analysis of HST images of M87 at multiple locations, and the observed kinematics of the M87 GCS.Our simulations also show that evolutionary processes significantly affect the initial GCS properties by leading to the disruption of many clusters and changing the masses of those which survive.The preferential disruption of inner clusters flattens the initial GCS number density profile and it can explain the rising specific frequency with radius; we show that the inner flattening observed in the M87 GCS spatial distribution can be the result of the effects of dynamical evolution on an initially steep density profile. (abridged)Comment: 15 pages,14 figures;accepted for publication in The Astrophysical Journa

Structure Formation Inside Triaxial Dark Matter Halos: Galactic Disks, Bulges and Bars

We investigate the formation and evolution of galactic disks immersed in assembling live DM halos. Disk/halo components have been evolved from the cosmological initial conditions and represent the collapse of an isolated density perturbation. The baryons include gas (which participates in star formation [SF]) and stars. The feedback from the stellar energy release onto the ISM has been implemented. We find that (1) The growing triaxial halo figure tumbling is insignificant and the angular momentum (J) is channeled into the internal circulation; (2) Density response of the disk is out of phase with the DM, thus diluting the inner halo flatness and washing out its prolateness; (3) The total J is neathly conserved, even in models accounting for feedback; (4) The specific J for the DM is nearly constant, while that for baryons is decreasing; (5) Early stage of disk formation resembles the cat's cradle -- a small amorphous disk fueled via radial string patterns; (6) The initially puffed up gas component in the disk thins when the SF rate drops below ~5 Mo/yr; (7) About 40%-60% of the baryons remain outside the SF region; (8) Rotation curves appear to be flat and account for the observed disk/halo contributions; (9) A range of bulge-dominated to bulgeless disks was obtained; Lower density threshold for SF leads to a smaller, thicker disk; Gravitational softening in the gas has a substantial effect on various aspects of galaxy evolution and mimics a number of intrinsic processes within the ISM; (10) The models are characterized by an extensive bar-forming activity; (11) Nuclear bars, dynamically coupled and decoupled form in response to the gas inflow along the primary bars.Comment: 18 pages, 16 figures, accepted by the Astrophysical Journal. Minor revisions. The high-resolution figures can be found at http://www.pa.uky.edu/~shlosman/research/galdyn/figs07a

Starbursts in multiple galaxy mergers

We numerically investigate stellar and gaseous dynamical evolution of mergers between five identical late-type disk galaxies with the special emphasis on star formation history and chemical evolution of multiple galaxy mergers. We found that multiple encounter and merging can trigger repetitive massive starbursts (typically $\sim$ 100 $M_{\odot}$ ${\rm yr}^{-1}$) owing to the strong tidal disturbance and the resultant gaseous dissipation during merging. The magnitude of the starburst is found to depend on initial virial ratio (i.e., the ratio of total kinematical energy to total potential energy) such that the maximum star formation rate is larger for the merger with smaller virial ratio. Furthermore we found that the time interval between the epochs of the triggered starbursts is longer for the merger with the larger virial ratio. The remnant of a multiple galaxy merger with massive starbursts is found to have metal-poor gaseous halo that is formed by tidal stripping during the merging. We accordingly suggest that metal-poor gaseous halo in a field elliptical galaxy is a fossil record of the past multiple merging events for the galaxy.Comment: 23 pages 16 figures,2000,ApJ,545 in press. For all ps figures, see http://newt.phys.unsw.edu.au/~bekki/res.dir/paper.dir/mul.dir/fig.tar.g

Gemini Spectroscopic Survey of Young Star Clusters in Merging/Interacting Galaxies. II. NGC 3256 Clusters

We present Gemini optical spectroscopy of 23 young star clusters in NGC3256. We find that the cluster ages range are from few Myr to ~150 Myr. All these clusters are relatively massive (2--40)x 10^{5} \msun$ and appear to be of roughly 1.5 \zo metallicity. The majority of the clusters in our sample follow the same rotation curve as the gas and hence were presumably formed in the molecular-gas disk. However, a western subsample of five clusters has velocities that deviate significantly from the gas rotation curve. These clusters may either belong to the second spiral galaxy of the merger or may have formed in tidal-tail gas falling back into the system. We discuss our observations in light of other known cluster populations in merging galaxies, and suggest that NGC 3256 is similar to Arp 220, and hence may become an Ultra-luminous Infrared Galaxy as the merger progresses and the star-formation rate increases. Some of the clusters which appeared as isolated in our ground-based images are clearly resolved into multiple sub-components in the HST-ACS images. The same effect has been observed in the Antennae galaxies, showing that clusters are often not formed in isolation, but instead tend to form in larger groups or cluster complexes.Comment: 20 pages, 10 figures, 3 tables; Accepted Ap

Dosage des polyphénols et activité anti-oxydante de feuilles et d’inflorescences mâles de Borassus aethiopum, Mart. (Arecaceae)

Borassus aethiopum est une plante de la famille des Arécacées. C’est un géant palmier qui présente un tronc dur appelé stipe, des racines fasciculées et des feuilles longues en forme d’éventail. Elle est presque cosmopolite et ses différentes parties sont utilisées dans nombreux domaines : économiques, écologiques,  alimentaires et sanitaire. En effet, sur le plan sanitaire, la pharmacopée utilise l’alcinât des feuilles en boisson dans l’eau pour traiter la bilharziose viscérale  (Sakande, 2004). L’objet de notre étude est de déterminer la teneur en polyphénols et de tester l’activité antioxydante d’extraits de feuilles en comparaison avec ceux des inflorescences mâles. Ainsi, la méthode colorimétrique de Folin Denis, décrite par Bassène (2012) a été utilisée pour le dosage des polyphénols. L’activité antioxydante a été déterminée par les méthodes chromatographique sur couche mince selon Takao et al. (1994) et colorimétrique décrite par Sakande (2004). Les teneurs en polyphénols totaux obtenues sont 13,56% et 5,6% Eq d’acide tannique respectivement dans les feuilles et les inflorescences mâles. Les teneurs  respectives en tanins dans les feuilles et les inflorescences mâles ont été évaluées à 13,46% et 5,47% Eq d’acide tannique. La chromatographie sur couche mince a révélé une activité antioxydante dans les extraits de feuilles et d’inflorescences mâles. Par la méthode colorimétrique utilisant le DPPH, les  résultats obtenus en mg Eq d’acide ascorbique sont 4 et 5 mg Eq respectivement dans les extraits d’acétate éthyle et butanolique de feuilles ; les extraits d’acétate d’éthyle et  butanolique  d’inflorescences mâles respectifs ont une activité antioxydante évaluée à 10 et 20 mgEq d’acide ascorbique. Les résultats obtenus de cette étude  montre que les extraits de feuilles ont des teneurs en polyphénols et en tanins supérieures à celles des extraits d’inflorescences mâles. L’activité antioxydante a été deux fois plus importante dans les extraits de feuilles que dans les extraits d’inflorescences mâles. Cependant, dans les feuilles l’extrait d’acétate d’éthyle  renferme deux fois plus de polyphénols et de tanins que l’extrait butanolique ; l’activité antioxydante est aussi plus élevée dans ce premier extrait.Mots clés : Borassus aethiopum, feuilles, inflorescences mâles, polyphénols, tanins, activité antioxydante