The Danish National Passenger Model – model specification and results

The paper describes the structure of the new Danish National Passenger model and provides on this basis a general discussion of large-scale model design, cost-damping and model validation. The paper aims at providing three main contributions to the existing literature. Firstly, at the general level, the paper provides a description of a large-scale forecast model with a discussion of the linkage between population synthesis, demand and assignment. Secondly, the paper gives specific attention to model specification and in particular choice of functional form and costdamping. Specifically we suggest a family of logarithmic spline functions and illustrate how it is applied in the model. Thirdly and finally, we evaluate model sensitivity and performance by evaluating the distance distribution and elasticities. In the paper we present results where the spline-function is compared with more traditional function types and it is indicated that the spline-function provides a better description of the data. Results are also provided in the form of a back-casting exercise where the model is tested in a back-casting scenario to 2002

Overall design of the Danish National transport model

The objective of the new Danish national transport model is to establish a unified reference model, which will form a new basis for transport policy analysis in Denmark. There are a number of important benefits by developing a single model framework rather than relying on a variety of regional models. Firstly, as different projects is compared using the same model, potential model bias will be ruled out. Secondly, as more resources can be put into the development of a single model, it can also be more comprehensive and advanced in a number of respects. Thirdly, it becomes much easier to maintain and update the data foundation, which is a very important issue in model development. The aim of the present paper is to outline the general model structure and to discuss how the model will be able to address a range of scenarios. More specifically, we will discuss how different model components are linked and briefly present the forecast methodology

Cool White Dwarfs Revisited -- New Spectroscopy and Photometry

In this paper we present new and improved data on 38 cool white dwarfs identified by Oppenheimer et al. 2001 (OHDHS) as candidate dark halo objects. Using the high-res spectra obtained with LRIS, we measure radial velocities for 13 WDs that show an H alpha line. We show that the knowledge of RVs decreases the UV-plane velocities by only 6%. The radial velocity sample has a W-velocity dispersion of sig_W = 59 km/s--in between the values associated with the thick disk and the stellar halo. We also see indications for the presence of two populations by analyzing the velocities in the UV plane. In addition, we present CCD photometry for half of the sample, and with it recalibrate the photographic photometry of the remaining WDs. Using the new photometry in standard bands, and by applying the appropriate color-magnitude relations for H and He atmospheres, we obtain new distance estimates. New distances of the WDs that were not originally selected as halo candidates yield 13 new candidates. On average, new distances produce velocities in the UV plane that are larger by 10%, with already fast objects gaining more. Using the new data, while applying the same UV-velocity cut (94 km/s) as in OHDHS, we find a density of cool WDs of 1.7e-4 pc^-3, confirming the value of OHDHS. In addition, we derive the density as a function of the UV-velocity cutoff. The density (corrected for losses due to higher UV cuts) starts to flatten out at 150 km/s (0.4e-4 pc^-3), and is minimized (thus minimizing a possible non-halo contamination) at 190 km/s (0.3e-4 pc^-3). These densities are in a rough agreement with the estimates for the stellar halo WDs, corresponding to a factor of 1.9 and 1.4 higher values.Comment: Accepted to ApJ. New version contains some additional data. Results unchange

The Masses of Population II White Dwarfs

Globular star clusters are among the first stellar populations to have formed in the Milky Way, and thus only a small sliver of their initial spectrum of stellar types are still burning hydrogen on the main-sequence today. Almost all of the stars born with more mass than 0.8 M_sun have evolved to form the white dwarf cooling sequence of these systems, and the distribution and properties of these remnants uniquely holds clues related to the nature of the now evolved progenitor stars. With ultra-deep HST imaging observations, rich white dwarf populations of four nearby Milky Way globular clusters have recently been uncovered, and are found to extend an impressive 5 - 8 magnitudes in the faint-blue region of the H-R diagram. In this paper, we characterize the properties of these population II remnants by presenting the first direct mass measurements of individual white dwarfs near the tip of the cooling sequence in the nearest of the Milky Way globulars, M4. Based on Gemini/GMOS and Keck/LRIS multiobject spectroscopic observations, our results indicate that 0.8 M_sun population II main-sequence stars evolving today form 0.53 +/- 0.01 M_sun white dwarfs. We discuss the implications of this result as it relates to our understanding of stellar structure and evolution of population II stars and for the age of the Galactic halo, as measured with white dwarf cooling theory.Comment: Accepted for Publication in Astrophys. J. on Aug. 05th, 2009. 19 pages including 9 figures and 2 tables (journal format

Biology and Biological Control of Exotic True Thistles

“Thistle” is an old English name for a large variety of weedy, prickly plants that grow throughout the world. The most notable characteristics of thistles are the prickly stems and leaves and the bracts around the flower head. While many different plants have “thistle” in their common name, only certain plant species fit the taxonomic requirements of being considered “true thistles.” True thistle species fall within the family Asteraceae, the tribe Cardueae, and the subtribe Carduinae. Examples of plants that are not true thistles include yellow starthistle (subtribe Centaureinae), sow thistle (subtribe Sonchinae), and Russian thistle (family Chenopodiaceae). Only true thistles in the subtribe Carduinae are discussed in this manual

Biology and Biological Control of Exotic True Thistles

“Thistle” is an old English name for a large variety of weedy, prickly plants that grow throughout the world. The most notable characteristics of thistles are the prickly stems and leaves and the bracts around the flower head. While many different plants have “thistle” in their common name, only certain plant species fit the taxonomic requirements of being considered “true thistles.” True thistle species fall within the family Asteraceae, the tribe Cardueae, and the subtribe Carduinae. Examples of plants that are not true thistles include yellow starthistle (subtribe Centaureinae), sow thistle (subtribe Sonchinae), and Russian thistle (family Chenopodiaceae). Only true thistles in the subtribe Carduinae are discussed in this manual

Chemical abundances in a high-velocity RR Lyrae star near the bulge

Low-mass variable high-velocity stars are interesting study cases for many aspects of Galactic structure and evolution. Until recently, the only known high- or hyper-velocity stars were young stars thought to originate from the Galactic center. Wide-area surveys such as APOGEE and BRAVA have found several low-mass stars in the bulge with Galactic rest-frame velocities higher than 350 km s-1. In this study we present the first abundance analysis of a low-mass RR Lyrae star that is located close to the Galactic bulge, with a space motion of ~–400 km s-1. Using medium-resolution spectra, we derived abundances (including upper limits) of 11 elements. These allowed us to chemically tag the star and discuss its origin, although our derived abundances and metallicity, at [Fe/H] =−0.9 dex, do not point toward one unambiguous answer. Based on the chemical tagging, we cannot exclude that it originated in the bulge. However, its retrograde orbit and the derived abundances combined suggest that the star was accelerated from the outskirts of the inner (or even outer) halo during many-body interactions. Other possible origins include the bulge itself, or the star might have been stripped from a stellar cluster or the Sagittarius dwarf galaxy when it merged with the Milky Way

Cattle grazing for invasive Phragmites australis (common reed) management in Northern Utah wetlands

This fact sheet provides suggestions for how cattle grazing can be integrated into Phragmites management programs in Northern Utah