The Initial Mass Function: Now and Then

We examine whether existing data in clusters, both old and young, and in the field of the Galactic disk and halo is consistent with a universal slope for the initial mass function (IMF). The most reasonable statement that can be made at the current time is that there is no strong evidence to support a claim of any real variations in this slope. If the IMF slope is universal then this in itself is remarkable implying that variations in metallicity, gas density or other environmental factors in the star formation process play no part in determining the slope of the mass function.Comment: 10 pages, postscript. To appear in "Proceedings 7th Annual Astrophysics Conference in Maryland-STAR FORMATION NEAR AND FAR

Rate Coefficients for the Collisional Excitation of Molecules: Estimates from an Artificial Neural Network

An artificial neural network (ANN) is investigated as a tool for estimating rate coefficients for the collisional excitation of molecules. The performance of such a tool can be evaluated by testing it on a dataset of collisionally-induced transitions for which rate coefficients are already known: the network is trained on a subset of that dataset and tested on the remainder. Results obtained by this method are typically accurate to within a factor ~ 2.1 (median value) for transitions with low excitation rates and ~ 1.7 for those with medium or high excitation rates, although 4% of the ANN outputs are discrepant by a factor of 10 more. The results suggest that ANNs will be valuable in extrapolating a dataset of collisional rate coefficients to include high-lying transitions that have not yet been calculated. For the asymmetric top molecules considered in this paper, the favored architecture is a cascade-correlation network that creates 16 hidden neurons during the course of training, with 3 input neurons to characterize the nature of the transition and one output neuron to provide the logarithm of the rate coefficient.Comment: 23 pages including 9 figures. Accepted for publication in Ap

Deep HST V- and I-Band Observations of Two Globular Clusters in the Halo of M31

We present deep (V ~= 27) V- and I-band stellar photometry of G302 and G312, two globular star clusters in the halo of M31. These data were obtained using the Hubble Space Telescope's Wide Field/Planetary Camera 2. We find iron abundances of [Fe/H] = -1.85 +/- 0.12 for G302 and [Fe/H] = -0.56 +/- 0.03 for G312, consistent with spectroscopic measurements. The color-magnitude diagrams for each cluster show no evidence for an intermediate-aged population of stars, or a second parameter effect in the morphology of the horizontal branch. G302 shows no evidence for a color gradient but the inner regions of G312 are bluer than the outer regions. G312 shows no evidence of ellipticity or an extended halo of unbound stars. G302 has a projected ellipticity of 0.195 +/- 0.012 with the projected major axis oriented towards the center of M31. G302 also shows evidence of an extended asymmetric stellar halo extending to at least twice the fitted Michie-King tidal radius. The amount of mass beyond the tidal radius of G302 is consistent with the stellar escape rates which have been predicted by N-body simulations of globular clusters in the Galactic tidal field.Comment: 29 pages, 21 Postscript figures, uses aaspp4.sty, to be published in the October 1997 A

The Double Cluster G185 in M31

We have identified a small globular cluster in M31 located approximately 4 arcseconds northwest of the M31 globular cluster G185. While several multiple globular clusters have been observed in the Magellanic Clouds none have been found in the Galaxy or in M31. We estimate the probability of such a chance line-of-sight alignment occuring near the nucleus of M31 to be 0.09 +/- 0.03 and find no obvious indication of any tidal deformation in either cluster, as would be expected if the clusters were interacting. Two-dimensional modelling suggests G185 has a King (1966) [AJ, 71, 64] concentration of c = 1.11 +/- 0.08 while the companion has c = 0.67 +/- 0.17 and is physically smaller than G185. Both objects have integrated dereddened colors similar to those of Galactic globular clusters.Comment: 22 pages, ~1Mb postscript file http://www.astro.ubc.ca/~holland/bib.html/ ftp://nukta.astro.ubc.ca/pub/holland/G185_preprint.ps.

Forum-Selection Clauses: Should State or Federal Law Determine Validity in Diversity Actions?—Stewart Organization, Inc. v. Ricoh Corp., 108 S. Ct. 2239 (1998)

Forum-selection clauses are contractual provisions that confine future litigation to particular courts. Such clauses are common in interstate contracts despite uncertainty concerning their validity. Before Stewart Organization, Inc. v. Ricoh Corp., the circuit courts were divided as to whether federal courts with diversity jurisdiction were compelled to determine forum-selection clause validity in accordance with state law, as directed by Erie R.R. Co. v. Tompkins. In Stewart, the United States Supreme Court ruled that federal courts did not have to apply state law. Instead, the court held that the federal transfer statute, 28 U.S.C. § 1404(a), governed forum-selection clause validity. A statutory interpretation analysis demonstrates 28 U.S.C. § 1404(a) was never intended to govern forum-selection clause validity. State law should govern the clause\u27s validity in order to prevent forum shopping and the inequitable administration of the laws

Advances in wildlife immobilisation and anaesthesia

Improvement of chemical capture is an important part of wildlife conservation and animal welfare to minimise distress for the animals and the risk of morbidity and mortality. The aim of this thesis was to improve wildlife immobilisation and anaesthesia by studying physiological variables and clinically evaluate different drug combinations and methods of capture in selected species. Reversible anaesthetic protocols were developed for use in free-ranging lions and four species of South- East Asian primates. Capture and anaesthesia of free-ranging wolverines, brown bears, black and white rhinoceros were physiologically evaluated. The effect of intranasal oxygen supplementation on arterial oxygenation was assessed in brown bears and rhinoceros. Partial reversal of the opioid effect and different body positions were evaluated in rhinoceros. Capture methods used included darting from a helicopter or the ground, and physical restraint followed by drug injection. Medetomidine-ketamine was used in wolverines and medetomidine-zolazepam-tiletamine in primates, lions and brown bears. Rhinoceros were immobilised with a combination of an opioid, azaperone and an alpha2-agonist. Body temperature and cardiorespiratory variables were monitored in all animals. Arterial blood samples were analysed to interpret pulmonary gas exchange and acid-base status in carnivores and rhinoceros. Low doses of medetomidine-zolazepam-tiletamine rapidly anaesthetised primates and lions, and reversal with atipamezole resulted in a smooth and calm recovery. Physiological alterations varied with different protocols and species and included changes in body temperature, respiratory and heart rates, gas exchange and acid-base balance. Hypoxaemia was recorded in all rhinoceros and most carnivore species. The major contributor to hypoxaemia was likely ventilation-perfusion mismatch including shunt. In rhinoceros, hypoventilation contributed to an impaired gas exchange and the animals remained hypoxaemic despite partial reversal. However, in black rhinoceros arterial oxygenation was higher during sternal compared to lateral recumbency. Capture-induced lactic acidaemia was recorded in carnivores and rhinoceros. Intranasal oxygen supplementation improved arterial oxygenation. In conclusion, this thesis increases the understanding of the effects of capture and anaesthesia in several wildlife species. Physiological derangements were identified, potential causative factors were investigated and methods for improvement were evaluated

Does Vision Need a Special-purpose Language?

Work reported herein was conducted at the Artificial Intelligence Laboratory, a Massachusetts Institute of Technology research program supported in part by the Advanced Research Projects Agency of the Department of Defense and monitored by the Office of Naval Research under Contract Number N00014-70-A-0362-0005. Vision Flashes are informal papers intended for internal use.This paper briefly discusses the following questions: What are the benefits of special-purpose languages? When is a field ready for such a language? Are any parts of our current vision research ready?MIT Artificial Intelligence Laborator