Tumbling asteroids

We present both a review of earlier data and new results on non-principal axis rotators (tumblers) among asteroids. Among new tumblers found, the best data we have are for 2002 TD60, 2000WL107, and (54789) 2001 MZ7—each of them shows a lightcurve with two frequencies (full terms with linear combinations of the two frequencies are present in the lightcurve). For 2002 TD60, we have constructed a physical model of the NPA rotation. Other recent objects which have been found to be likely tumblers based on their lightcurves that do not fit with a single periodicity are 2002 NY40, (16067) 1999 RH27, and (5645) 1990 SP. We have done a statistical analysis of the present sample of the population of NPA rotators. It appears that most asteroids larger than ~ 0.4 km with estimated damping timescales (Harris, 1994, Icarus 107, 209) of 4.5 byr and longer are NPA rotators. The statistic of two short-period tumblers (D = 0.04 and 0.4 km) with non-zero tensile strength suggests that for them the quantity μQ/T , where μ is the mechanical rigidity, Q is the elastic dissipation factor, and T is a spin excitation age (i.e., a time elapsed since the last significant spin excitation event), is greater by two to four orders of magnitude than the larger, likely rubble-pile tumblers. Among observational conditions and selection effects affecting detections of NPA rotations, there is a bias against detection of low-amplitude (small elongation) tumblers

A Primer on Governance and Performance in Small- and Medium-Sized Enterprises

This paper is a primer on corporate performance, corporate governance, and their interrelationships and measurement systems, with particular focus on Small and Medium- Sized Enterprises (SMEs). This is the first report of a larger on going research project. In the domain of performance measurement the paper describes the trend from financial to non-financial measures, as well as a taxonomy of measures and the impact of the TQM movement on measurement practices. In the domain of governance, governance as a general concept is presented, followed by the more specific concept of corporate governance. Four theories of corporate governance are explained, along with literature findings on the relationship between corporate governance and corporate performance, with reference to both works on large firms and works on SMEs