Author Correction: Laser-wakefield accelerators for high-resolution X-ray imaging of complex microstructures.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Laser-wakefield accelerators for high-resolution X-ray imaging of complex microstructures.

Laser-wakefield accelerators (LWFAs) are high acceleration-gradient plasma-based particle accelerators capable of producing ultra-relativistic electron beams. Within the strong focusing fields of the wakefield, accelerated electrons undergo betatron oscillations, emitting a bright pulse of X-rays with a micrometer-scale source size that may be used for imaging applications. Non-destructive X-ray phase contrast imaging and tomography of heterogeneous materials can provide insight into their processing, structure, and performance. To demonstrate the imaging capability of X-rays from an LWFA we have examined an irregular eutectic in the aluminum-silicon (Al-Si) system. The lamellar spacing of the Al-Si eutectic microstructure is on the order of a few micrometers, thus requiring high spatial resolution. We present comparisons between the sharpness and spatial resolution in phase contrast images of this eutectic alloy obtained via X-ray phase contrast imaging at the Swiss Light Source (SLS) synchrotron and X-ray projection microscopy via an LWFA source. An upper bound on the resolving power of 2.7 ± 0.3 µm of the LWFA source in this experiment was measured. These results indicate that betatron X-rays from laser wakefield acceleration can provide an alternative to conventional synchrotron sources for high resolution imaging of eutectics and, more broadly, complex microstructures.

Benefits of an exercise class for elderly women following hip surgery.

A prospective cohort study of a twice weekly exercise programme for six months was undertaken to determine the benefits of an exercise class for 28 elderly women following hip surgery. The effects of the exercise programme were monitored using cycle ergometry. Walking speed was measured on entry and at 3, 6 and 12 months. Twenty-six subjects completed the programme with an overall attendance rate of 88%. Measures of fitness, calculated from cycle ergometry, did not improve significantly apart from test duration. In contrast there was a significant improvement in mean walking speed, with a 50% increase between 0 and 3 months and a further 21% increase between 3 and 6 months. This improvement was maintained at 12 months.

The effect of minimal exercise on fitness in elderly women after hip surgery.

To determine the effect of minimal exercise on functional fitness following total hip replacement in elderly women, 20 women (13 exercisers, 7 controls) who had undergone unilateral or bilateral hip replacement surgery for primary osteoarthritis were studied. An exercise treadmill test with respiratory gas and blood lactate analyses, and a field test of walking speed on a measured course, were administered before and after a twice weekly exercise programme of three months' duration. Markers of cardiorespiratory fitness, including peak achieved oxygen uptake (VO2) and ventilatory and lactate thresholds were measured. Maximum self-selected walking speed was also measured over a flat course. Peak VO2 increased in the exercise group when compared to baseline (P < 0.05) but did not differ from the control group. The exercise group significantly improved their walking speed by 10.1% compared with non-exercising controls (1.41 vs 1.20 m/sec, P < 0.05), and increased VO2 at lactate threshold. The improvements occurred despite the twice weekly exercise sessions being below the recommended frequency of exercise for improving cardiorespiratory fitness. Minimal exercise in elderly women after hip surgery can substantially improve submaximal exercise capacity, as well as walking speed.

Effects of chair design, age and cognitive status on mobility.

To test the validity of published guidelines on the height of seating for the elderly, ambulant residents in three Social Services' Homes were asked to rise from their usual chairs and from a chair conforming to the guidelines. When both seat and arm height were at recommended levels, 77% of those who were usually chair-fast could rise unaided. More agile residents also benefited, as they could rise with less difficulty. Though mobility decreased with age, those who failed to benefit were distinguished by advanced brain failure rather than age. Some aspects of cost are discussed.