Individual calibration for estimating free-living walking speed using the MTI monitor

Purpose : This study was conducted to devise a new individual calibration method to enhance MTI accelerometer estimation of free-living level walking speed.

Method : Five female and five male middle-aged adults walked 400 m at 3.5, 4.5, and 5.5 km·h-1, and 800 m at 6.5 km·h-1 on an outdoor track, following a continuous protocol. Lap speed was controlled by a global positioning system (GPS) monitor. MTI counts-to-speed calibration equations were derived for each trial, for each subject for four such trials with each of four MTI, for each subject for the average MTI, and for the pooled data. Standard errors of the estimate (SEE) with and without individual calibration were compared. To assess accuracy of prediction of free-living walking speed, subjects also completed a self-paced, "brisk" 3-km walk wearing one of the four MTI, and differences between actual and predicted walking speed with and without individual calibration were examined.

Results : Correlations between MTI counts and walking speed were 0.90 without individual calibration, 0.98 with individual calibration for the average MTI, and 0.99 with individual calibration for a specific MTI. The SEE (mean ± SD) was 0.58 ± 0.30 km·h-1 without individual calibration, 0.19 ± 0.09 km·h-1 with individual calibration for the average MTI monitor, and 0.16 ± 0.08 km·h-1 with individual calibration for a specific MTI monitor. The difference between actual and predicted walking speed on the "brisk" 3-km walk was 0.06 ± 0.25 km·h-1 using individual calibration and 0.28 ± 0.63 km·h-1 without individual calibration (for specific accelerometers).

Conclusion : MTI accuracy in predicting walking speed without individual calibration might be sufficient for population-based studies but not for intervention trials. This individual calibration method will substantially increase precision of walking speed predicted from MTI counts.

The volume of water filtered by a Continuous Plankton Recorder sample: the effect of ship speed

The Continuous Plankton Recorder (CPR) survey is one of the largest plankton-monitoring programmes in the world. Since 1931, the CPR has collected ∼380 000 samples, each representing 10 miles of tow. It has been assumed that the volume of seawater filtered by each sample remained constant and close to 3 m3. In this study, the volume filtered for each CPR sample was measured on two routes (SA and IN), monitored by the CPR survey, between 1995 and 2000. Although the filtered volume was near the theoretical value of 3 m3 on the SA route (3.2 m3), it was significantly higher on the IN route (3.8 m3). A significant negative relationship was found between the volume filtered and the speed of the ships. This relationship indicates that the faster the speed of the ship, the lower the volume filtered. This could have implications for the CPR survey as the speed of the ships has increased continuously since the end of the 1950s. However, no significant correlation was found between the long-term changes in the speed of the ships and two commonly used indicators of plankton variability: the Phytoplankton Colour and the Total Copepods indices. This absence of relationship may indicate that the effect found is small in comparison with the influence of hydroclimatic forcing, although a more extensive study is needed to confirm these findings.

Spinoza/space/speed/sublime: Problems of philosophy and politics in the post-colonial fiction of Gerald Murnane

This article takes account of the ‘spontaneity’ of the post-colonial fiction of Gerald Murnane within the ‘dominating space’ of the philosophy of Spinoza. My use of Paul Carter’s terms here is strategic. The compact of fiction and philosophy in Murnane corresponds with the relationship of spontaneity to the dominating organization of desire in Carter’s rendering of an Aboriginal hunter. Carter’s phrase “‘a figure at once spontaneous and wholly dominated by the space of his desire’” worries Ken Gelder and Jane M. Jacobs, who suggest that it subjugates the formation of Aboriginal desire (incorporating spontaneity) to impulses of imperialism. The captivating immanence of Spinoza’s philosophy in Murnane’s fiction, which I will demonstrate with various examples, puts pressure on the fiction to occupy the same space as the space of the philosophy. Here is a clue to why Murnane’s post-colonial thematics have been little explored by critics with an interest in post-colonial politics. The desire of Spinoza’s philosophy creates a spatial textuality within which the spontaneity of Murnane’s fiction, to the degree that it maximizes or fills the philosophy, is minimized in its political effects. That is to say, the fiction shifts politics into an external space of what Roland Barthes calls “resistance or condemnation”. However, the different speeds (or timings) of Murnane and Spinoza, within the one space, mitigate this resistance of the outside, at least in respect of certain circumstances of post-coloniality. It is especially productive, I suggest, to engage Carter’s representation of an Aboriginal hunter through the compact of coincidental spaces and differential speeds created by Murnane’s fiction in Spinoza’s philosophy. This produces a ceaseless activation of desire and domination, evidenced in Murnane’s short story ‘Land Deal’, and indexed by a post-Romantic sublime. What limits the value of Murnane’s fiction in most contexts of post-colonial politics, is precisely what makes it useful in the matter of Carter’s Aboriginal hunter.