Globular Cluster Population of Hickson Compact Group 22a and 90c

We present the first measurement of the globular cluster populations of galaxies in Hickson compact groups, in order to investigate the effect of these high density environments on the formation and evolution of globular cluster systems. Based on V and R band images that we obtained of HCG 22a and HCG 90c with the ESO New Technology Telescope (NTT), we find a total globular cluster population of $1590\pm 854$ for HCG 22a and $2136\pm 718$ for 90c. The specific frequency for HCG 22a was found to be $S_{N}=1.9\pm 1.0$ and $S_{N}= 3.4\pm 1.1$ for HCG 90c. A power-law fit to the globular cluster radial profile of HCG 22a yields $\sigma\sim R^{-2.01\pm 0.30}$ and for HCG 90c we found $\sigma \sim R^{-1.20\pm0.16}$. A comparison of the globular cluster radial profiles with the surface brightness of the parent galaxy shows that the globular cluster systems are at least as extended as the halo light. The measured values for the specific frequency are consistent with a scenario in which the host galaxies were in a low density ``field-like'' environment when they formed their globular cluster systems.Comment: 28 pages, 13 figures, 3 tables, accepted for publication in the Astrophysical Journa

Gate-to-Gate Life-Cycle Inventory of Softwood Lumber Production

To perform a life-cycle analysis, a life-cycle inventory is needed. Data from surveys of manufacturers are presented for the energy and materials required to produce 1.623 m3 (1 mbf) of planed, dry, dimension lumber from logs in the western and southern U.S. In the West and South, 53 and 41% of the log volume (3.05 and 3.92 m3) leaves the mill as planed, dry dimension lumber, respectively. A much greater portion of the energy used for production in the South is produced on site from wood fuels. CO2 emissions were greater in the South because of the wood fuel, 574 kg versus 419 kg per 1.623 m3 produced

Intergalactic Globular Clusters

We confirm and extend our previous detection of a population of intergalactic globular clusters in Abell 1185, and report the first discovery of an intergalactic globular cluster in the nearby Virgo cluster of galaxies. The numbers, colors and luminosities of these objects can place constraints on their origin, which in turn may yield new insights to the evolution of galaxies in dense environments.Comment: 2 pages, no figures. Talk presented at JD6, IAU General Assembly XXV, Sydney, Australia, July 2003, to appear in Highlights of Astronomy, Vol. 1

A high sensitivity momentum flux measuring instrument for plasma thruster exhausts and diffusive plasmas

A high sensitivity momentum flux measuring instrument based on a compound pendulum has been developed for use with electric propulsion devices and radio frequency driven plasmas. A laser displacement system, which builds upon techniques used by the materials science community for surface stress measurements, is used to measure with high sensitivity the displacement of a target plate placed in a plasma thruster exhaust. The instrument has been installed inside a vacuum chamber and calibrated via two different methods and is able to measure forces in the range of 0.02-0.5 mN with a resolution of 15 microN. Measurements have been made of the force produced from the cold gas flow and with a discharge ignited using argon propellant. The plasma is generated using a Helicon Double Layer Thruster prototype. The instrument target is placed about 1 mean free path for ion-neutral charge exchange collisions downstream of the thruster exit. At this position, the plasma consists of a low density ion beam (10%) and a much larger downstream component (90%). The results are in good agreement with those determined from the plasma parameters measured with diagnostic probes. Measurements at various flow rates show that variations in ion beam velocity and plasma density and the resulting momentum flux can be measured with this instrument. The instrument target is a simple, low cost device, and since the laser displacement system used is located outside the vacuum chamber, the measurement technique is free from radio frequency interference and thermal effects. It could be used to measure the thrust in the exhaust of other electric propulsion devices and the momentum flux of ion beams formed by expanding plasmas or fusion experiments

'A Better Way to Measure Choices' Discrete Choice Experiment and Conjoint Analysis Studies in Nephrology: A Literature Review

Discrete choice experiments (DCE) and conjoint analysis (CA) are increasingly used to address health policy issues. This is because the DCE and CA approaches have theoretical foundations in the characteristics theory of demand, which assumes goods, services, or healthcare provision, can be valued in terms of their characteristics (or attributes). As a result, such analysis is grounded in economic theory, lending theoretical validity to this approach. With DCEs, respondents are also assumed to act in a utility-maximising manner and make choices contingent upon the levels of attributes in DCE scenarios. Therefore, choice data can be analysed using econometric methods compatible with random utility theory (RUT) or random regret minimisation (RRM) theory. This means they have additional foundations in economic theory. In contrast, analyses described as CAs are sometimes compatible with RUT or RRM, but by definition they do not have to be. In this paper we review the CA/DCE evidence relating to nephrology. The CA/DCE approach is then compared with other approaches used to provide either quality of life information or preference information relating to nephrology. We conclude by providing an assessment of the value of undertaking CA or DCE analysis in nephrology, comparing the application of CA/DCEs in nephrology with other methodological approaches.</p