7,343 research outputs found
Modelling on Industrial Robots - Comparing and exploring different methods to program industrial robots
Reconciling dwarf galaxies with LCDM cosmology: Simulating a realistic population of satellites around a Milky Way-mass galaxy
Low-mass "dwarf" galaxies represent the most significant challenges to the
cold dark matter (CDM) model of cosmological structure formation. Because these
faint galaxies are (best) observed within the Local Group (LG) of the Milky Way
(MW) and Andromeda (M31), understanding their formation in such an environment
is critical. We present first results from the Latte Project: the Milky Way on
FIRE (Feedback in Realistic Environments). This simulation models the formation
of a MW-mass galaxy to z = 0 within LCDM cosmology, including dark matter, gas,
and stars at unprecedented resolution: baryon particle mass of 7070 Msun with
gas kernel/softening that adapts down to 1 pc (with a median of 25 - 60 pc at z
= 0). Latte was simulated using the GIZMO code with a mesh-free method for
accurate hydrodynamics and the FIRE-2 model for star formation and explicit
feedback within a multi-phase interstellar medium. For the first time, Latte
self-consistently resolves the spatial scales corresponding to half-light radii
of dwarf galaxies that form around a MW-mass host down to Mstar > 10^5 Msun.
Latte's population of dwarf galaxies agrees with the LG across a broad range of
properties: (1) distributions of stellar masses and stellar velocity
dispersions (dynamical masses), including their joint relation; (2) the
mass-metallicity relation; and (3) a diverse range of star-formation histories,
including their mass dependence. Thus, Latte produces a realistic population of
dwarf galaxies at Mstar > 10^5 Msun that does not suffer from the "missing
satellites" or "too big to fail" problems of small-scale structure formation.
We conclude that baryonic physics can reconcile observed dwarf galaxies with
standard LCDM cosmology.Comment: 7 pages, 5 figures. Accepted for publication in ApJ Letters. Several
updates, including: (1) fixed a bug in halo finder, now identifies 13
satellite galaxies and more subhalos in the baryonic simulation; (2) fixed a
minor bug in the feedback coupling and reran the simulation, resulting in a
somewhat lower-mass host galaxy; (3) Fig 2 now shows stellar velocity
dispersion profiles of satellite
- A Baumol-Tobin approach to money demand
Master's thesis in FinanceWe study which variables can explain the demand for cash across countries. Our study is based on 11 years of data for 45 countries ranging from low income to high income. As expected, we find that GDP per capita is positively related to cash per capita, and interest rates are negatively related to cash per capita. Next, we explore whether various measures of country risk (or alternatively, various measures of country’s institutional quality) are related to demand for cash. Our results indicate that the country risk variables do not impact the demand for money. However, we find some evidence that Democratic accountability has negative impact on cash holdings, while Government stability has positive impact
Preserving a Comprehensive Vegetation Knowledge Base - An Evaluation of Four Historical Soviet Vegetation Maps of the Western Pamirs (Tajikistan)
Vanselow KA, Samimi C, Breckle S-W. Preserving a Comprehensive Vegetation Knowledge Base - An Evaluation of Four Historical Soviet Vegetation Maps of the Western Pamirs (Tajikistan). PLOS ONE. 2016;11(2): e0148930.We edited, redrew, and evaluated four unpublished historical vegetation maps of the Western Pamirs (Tajikistan) by the Soviet geobotanist Okmir E. Agakhanjanz. These maps cover an area of 5,188 km(2) and date from 1958 to 1960. The purpose of this article is to make the historic vegetation data available to the scientific community and thus preserve a hitherto non available and up to now neglected or forgotten data source with great potential for studies on vegetation and ecosystem response to global change. The original hand-drawn maps were scanned, georeferenced, and digitized and the corresponding land cover class was assigned to each polygon. The partly differing legends were harmonized and plant names updated. Furthermore, a digital elevation model and generalized additive models were used to calculate response curves of the land cover classes and to explore vegetation-topography relationships quantitatively. In total, 2,216 polygons belonging to 13 major land cover classes were included that are characterized by 252 different plant species. As such, the presented maps provide excellent comparison data for studies on vegetation and ecosystem change in an area that is deemed to be an important water tower in Central Asia
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