Progress in science is dependent upon, and frequently follows, the development of new measurement techniques. In the context of controlled trials of physiotherapeutic techniques, the major requirements are that any measure should be: valid, reliable when used by different observers, simple enough to be used on patients who are often old and suffering other problems, and sensitive enough to detect clinically significant differences. This paper discusses measures of arm function which might fulfil these criteria.

We present analysis of MACHO Alert 95-30, a dramatic gravitational microlensing event towards the Galactic bulge whose peak magnification departs significantly from the standard point-source microlensing model. Alert 95-30 was observed in real-time by the Global Microlensing Alert Network (GMAN), which obtained densely sampled photometric and spectroscopic data throughout the event. We interpret the light-curve "fine structure" as indicating transit of the lens across the extended face of the source star. This signifies resolution of a star several kpc distant.We find a lens angular impact parameter θ min /θ source = 0.715 ± 0.003. This information, along with the radius and distance of the source, provides an additional constraint on the lensing system. Spectroscopic and photometric data indicate the source is an M4 III star of radius 61 ± 12R ⊙ , located on the far side of the bulge at ∼ 9 kpc. We derive a lens angular velocity, relative to the source, of 21.5 ± 4.9 km s −1 kpc −1 , where the error is dominated by uncertainty in the source radius. Likelihood analysis yields a median lens mass of 0.67 +2.53 −0.46 M ⊙ , located with 80% probability in the Galactic bulge at a distance of 6.93 +1.56 −2.25 kpc. If the lens is a main-sequence star, we can include constraints on the lens luminosity. This modifies our estimates to M lens = 0.53 +0.52 −0.35 M ⊙ and D lens = 6.57 +0.99 −2.25 kpc. Spectra taken during the event show that the absorption line equivalent widths of Hα and the TiO bands near 6700Å vary, as predicted for microlensing of an extended source. This is most likely due to center-to-limb variation in the stellar spectral lines. The observed spectral changes further support our microlensing interpretation. These data demonstrate the feasibility of using microlensing limb crossings as a tool to probe stellar atmospheres directly.Subject headings: dark matter -gravitational lensing -stars: low-mass, brown dwarfsstars: late-type -stars: atmospheres Table 4. Photometry of the source star in MACHO 95-30Observed Extinction Dereddened Abs Mag, 8 kpc Abs Mag, 9 kpc V = 16.21 A V = 1.35 V 0 = 14.86 M V = +0.34 M V = +0.59 K = 9.98 A K = 0.15 K 0 = 9.83 M K = −4.69 M K = −4.45 V − R = 1.39 E(V − R) = 0.34 V − R 0 = 1.05 J − K = 1.12 E(J − K) = 0.23 J − K 0 = 0.89 H − K = 0.26 E(H − K) = 0.08 H − K 0 = 0.18 V − K = 6.23 E(V − K) = 1.21 V − K 0 = 5.03 Bolometric BC K = −2.7 ± 0.1 M bol = −2.0 M bol = −2.25

We present the lightcurves of 21 gravitational microlensing events from the first six years of the MACHO Project gravitational microlensing survey which are likely examples of lensing by binary systems. These events were manually selected from a total sample of ~350 candidate microlensing events which were either detected by the MACHO Alert System or discovered through retrospective analyses of the MACHO database. At least 14 of these 21 events exhibit strong (caustic) features, and 4 of the events are well fit with lensing by large mass ratio (brown dwarf or planetary) systems, although these fits are not necessarily unique. The total binary event rate is roughly consistent with predictions based upon our knowledge of the properties of binary stars, but a precise comparison cannot be made without a determination of our binary lens event detection efficiency. Towards the Galactic bulge, we find a ratio of caustic crossing to non-caustic crossing binary lensing events of 12:4, excluding one event for which we present 2 fits. This suggests significant incompleteness in our ability to detect and characterize non-caustic crossing binary lensing. The distribution of mass ratios, N(q), for these binary lenses appears relatively flat. We are also able to reliably measure source-face crossing times in 4 of the bulge caustic crossing events, and recover from them a distribution of lens proper motions, masses, and distances consistent with a population of Galactic bulge lenses at a distance of 7 +/- 1 kpc. This analysis yields 2 systems with companions of ~0.05 M_sun.Comment: 83 pages, including 5 tables and 48 figures; submitted to The Astrophysical Journal. Data will soon be available at http://wwwmacho.mcmaster.ca/ and http://wwwmacho.anu.edu.au

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We investigate the assumption that the trigger of star formation in dwarf galaxies is interactions with other galaxies, in the context of a search for a ‘primary’ trigger of a first generation of stars. This is cosmologically relevant because the galaxy formation process consists not only of the accumulation of gas in a gravitational potential well but also of the triggering of star formation in this gas mass, and also because some high‐z potentially primeval galaxy blocks look like nearby star‐forming dwarf galaxies. We review theoretical ideas proposed to account for the tidal interaction triggering mechanism and present a series of observational tests of this assumption using published data. We also show results of a search in the vicinity of a composite sample of 96 dwarf late‐type galaxies for interaction candidates showing star formation. The small number of possible perturbing galaxies identified in the neighbourhood of our sample galaxies, along with similar findings from other studies, supports the view that tidal interactions may not be relevant as primary triggers of star formation. We conclude that interactions between galaxies may explain some forms of star formation triggering, perhaps in central regions of large galaxies, but they do not seem to be significant for dwarf galaxies and, by inference, for first‐time galaxies forming at high redshifts. Intuitive reasoning, based on an analogy with stellar dynamics, shows that conditions for primary star formation triggering may occur in gas masses oscillating in a dark‐matter gravitational potential. We propose this mechanism as a plausible primary trigger scenario, which would be worth investigating theoretically.