Plasticity of Alarm-call Response Development in Belding’s Ground Squirrels ( Spermophilus beldingi , Sciuridae)

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72444/1/j.1439-0310.1999.00389.x.pd

The Velocity Dispersion Profile of the Remote Dwarf Spheroidal Galaxy Leo I: A Tidal Hit and Run?

(abridged) We present kinematic results for a sample of 387 stars located near Leo I based on spectra obtained with the MMT's Hectochelle spectrograph near the MgI/Mgb lines. We estimate the mean velocity error of our sample to be 2.4 km/s, with a systematic error of < 1 km/s. We produce a final sample of 328 Leo I red giant members, from which we measure a mean heliocentric radial velocity of 282.9 +/- 0.5 km/s, and a mean radial velocity dispersion of 9.2 +/- 0.4 km/s for Leo I. The dispersion profile of Leo I is flat out to beyond its classical `tidal' radius. We fit the profile to a variety of equilibrium dynamical models and can strongly rule out models where mass follows light. Two-component Sersic+NFW models with tangentially anisotropic velocity distributions fit the dispersion profile well, with isotropic models ruled out at a 95% confidence level. The mass and V-band mass-to-light ratio of Leo I estimated from equilibrium models are in the ranges 5-7 x 10^7 M_sun and 9-14 (solar units), respectively, out to 1 kpc from the galaxy center. Leo I members located outside a `break radius' (about 400 arcsec = 500 pc) exhibit significant velocity anisotropy, whereas stars interior appear to have isotropic kinematics. We propose the break radius represents the location of the tidal radius of Leo I at perigalacticon of a highly elliptical orbit. Our scenario can account for the complex star formation history of Leo I, the presence of population segregation within the galaxy, and Leo I's large outward velocity from the Milky Way. The lack of extended tidal arms in Leo I suggests the galaxy has experienced only one perigalactic passage with the Milky Way, implying that Leo I may have been injected into its present orbit by a third body a few Gyr before perigalacticon.Comment: ApJ accepted, 23 figures, access paper as a pdf file at http://www.astro.lsa.umich.edu/~mmateo/research.htm

On Kinematic Substructure in the Sextans Dwarf Spheroidal Galaxy

We present multifiber echelle radial velocity results for 551 stars in the Sextans dwarf spheroidal galaxy and identify 294 stars as probable Sextans members. The projected velocity dispersion profile of the binned data remains flat to a maximum angular radius of $30^{\prime}$. We introduce a nonparametric technique for estimating the projected velocity dispersion surface, and use this to search for kinematic substructure. Our data do not confirm previous reports of a kinematically distinct stellar population at the Sextans center. Instead we detect a region near the Sextans core radius that is kinematically colder than the overall Sextans sample with 95% confidence.Comment: accepted for publication in ApJ Letters; 4 figures (2 color

The Case Against Cosmology

It is argued that some of the recent claims for cosmology are grossly overblown. Cosmology rests on a very small database: it suffers from many fundamental difficulties as a science (if it is a science at all) whilst observations of distant phenomena are difficult to make and harder to interpret. It is suggested that cosmological inferences should be tentatively made and sceptically received.Comment: 9 pages, no figure

Masses for the Local Group and the Milky Way

We use the very large Millennium Simulation of the concordance $\Lambda$CDM cosmogony to calibrate the bias and error distribution of Timing Argument estimators of the masses of the Local Group and of the Milky Way. From a large number of isolated spiral-spiral pairs similar to the Milky Way/Andromeda system, we find the interquartile range of the ratio of timing mass to true mass to be a factor of 1.8, while the 5% and 95% points of the distribution of this ratio are separated by a factor of 5.7. Here we define true mass as the sum of the ``virial'' masses $M_{200}$ of the two dominant galaxies. For current best values of the distance and approach velocity of Andromeda this leads to a median likelihood estimate of the true mass of the Local Group of 5.27\times 10^{12}\msun, or $\log M_{LG}/M_\odot = 12.72$, with an interquartile range of $[12.58, 12.83]$ and a 5% to 95% range of $[12.26, 13.01]$. Thus a 95% lower confidence limit on the true mass of the Local Group is 1.81\times 10^{12}\msun. A timing estimate of the Milky Way's mass based on the large recession velocity observed for the distant satellite Leo I works equally well, although with larger systematic uncertainties. It gives an estimated virial mass for the Milky Way of 2.43 \times 10^{12}\msun with a 95% lower confidence limit of 0.80 \times 10^{12}\msun.Comment: 11 pages, 6 figures, MNRAS accepted. Added a new discussion paragraph and a new figure regarding the relative transverse velocity but conclusions unchange

Dark matter annihilation and decay profiles for the Reticulum II dwarf spheroidal galaxy

The dwarf spheroidal galaxies (dSph) of the Milky Way are among the most attractive targets for indirect searches of dark matter. In this work, we reconstruct the dark matter annihilation (J-factor) and decay profiles for the newly discovered dSph Reticulum II. Using an optimized spherical Jeans analysis of kinematic data obtained from the Michigan/Magellan Fiber System (M2FS), we find Reticulum II's J-factor to be among the largest of any Milky Way dSph. We have checked the robustness of this result against several ingredients of the analysis. Unless it suffers from tidal disruption or significant inflation of its velocity dispersion from binary stars, Reticulum II may provide a unique window on dark matter particle properties.Comment: 5 pages, 4 figures. Match the ApJL accepted versio

Quiste gaseoso intrarraquídeo lumbar con síndrome radicular asociado: aportación de cuatro casos

Los autores aportan cuatro casos de síndrome radicular secundarios a una compresión radicular por quiste gaseosos intrarraquídeo extradural. El método de diagnóstico ha sido exploración con TAC y con RM. La presencia de gas intrarraquídeo es discutido en la bibliografía revisada.The authors describe four cases of secondary radicular syndrome due to radicular compression by a gas-containing cyst in the extradural space. The diagnosis was made by CT-Scan and MR imaging. The pathogenesis of the presence of epidural gas is discussed in the literature reviewed

EGNOS Terrestrial Regional Augmentation Networks Based on AIS for River Information Services

Within the ESA Advanced Research Telecommunications program ARTES-5, the project GALEWAT (Galileo and EGNOS for Waterway Transport) aims at introducing EGNOS into River Information Services (RIS) through the Automatic Identification System (AIS), a link that is mandatory for seagoing vessels above 300 GT. The GALEWAT project comprises several phases: During the initial definition phase, the system architecture and user equipment have been defined in line with standards and international recommendations. This phase was followed by the implementation phase, aiming at developing and setting up the equipment. Finally, the project will be completed by an extensive demonstration phase, which is currently under execution. Up to now, public GALEWAT demonstrations in Vienna (Austria), and Lisbon (Portugal) have been successfully executed. The last demonstration in Constanta (Romania) will take place in fall 2005. These demonstration sites have been chosen to test and demonstrate the GALEWAT system in different environments: river navigation, harbour approach, and open sea operations. The paper gives a short idea of River Information Services and an overview of the GALEWAT project. The main part concentrates on the presentation of field measurement results, which were collected in Lisbon, to show the performance of the GALEWAT concept. Finally, the paper presents an overview of user feedback resulting from the first two public demonstrations. Reprinted with permission from The Institute of Navigation (http://ion.org/) and The Proceedings of the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation, (pp. 827-832). Fairfax, VA: The Institute of Navigation

Growth performance, recovery rate and fish yield of GIFT strain at various water depths under rice-fish culture systems

Effect of water depth on recovery rate, growth performance and fish yield of GIFT in the rice-fish production systems was studies in experimental plots of 123 m2 with a pond refuge of I meter deep which covered 10% of the total land area. Mortality rate of fish was very low ranging from 0.81-1.63%. However, at harvest, recovery rate ranged from 76.69-82.93% with the highest recovery at 11-15 em of water depth. Significantly the highest absolute growth (99.97) and specific growth rate (2.42%) were found at 21-25 cm water depth. The same treatment also produced significantly higher fish yield (909.76 kg/ha) although statistically similar to the fish yield (862.60 kg/ha) obtained at ll-15 em of water depth. Results also suggested that higher water depth can produce bigger fish but no significant effects of water depth was found on fish yield in the treatments 11-15 cm and 21-25 cm water depths of this experiment