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BackgroundOlder individuals have been shown to present muscle atrophy in conjunction with increased fat fraction in some muscles. The proportion of fat and connective tissue within the skeletal muscle can be estimated from axial B-mode ultrasound images using echo intensity (EI). EI was used to calculate the index of muscle quality. Walking, home-based weight-bearing resistance training, and its combinations are considered simple, easy, and practical exercise interventions for older adults. The purpose of this study was to quantify the effects of walking and walking with home-based resistance training on muscle quality of older individuals.MethodsThirty-one participants performed walking training only (W-group; 72 ± 5 years) and 33 participants performed walking and home-based resistance training (WR-group; 73 ± 6 years). This study was a non-randomized controlled trial with no control group. All participants were instructed to walk 2 or 3 sets per week for 10 weeks (one set: 30-min continuous walking). In addition, the WR-group performed home-based weight-bearing resistance training. EI was measured as a muscle quality index using axial B-mode ultrasound images of the rectus femoris and vastus lateralis of the mid-thigh. We further averaged these parameters to obtain the EI of the quadriceps femoris (QF). Participants further performed five functional tests: sit-ups, supine up, sit-to-stand, 5-m maximal walk, and 6-min walk.ResultsQF EI was significantly decreased in both groups after training (W-group 69.9 ± 7.4 a.u. to 61.7 ± 7.0 a.u., WR-group 64.0 ± 9.5 a.u. to 51.1 ± 10.0 a.u.; P < 0.05), suggesting improved muscle quality. QF EI was further decreased in the WR-group compared with the W-group. The sit-up test in both groups and the sit-to-stand and 5-m maximal walk tests in the W-group were significantly improved after training.ConclusionThese results suggest that training-induced stimulation is associated with a decrease in EI in some thigh regions. Furthermore, the addition of home-based resistance training to walking would be effective for a greater reduction of EI.

The present results indicate that EFOV ultrasound imaging has high repeatability for measuring CSA and echo intensity of abdominal skeletal muscle groups in healthy college-aged males.

In the JIPP T-IIU tokamak an experiment to demonstrate the feasibility of fast wave current drive using five loop antennas has been successfully carried out with a relatively high density plasma (ωpe2/ωce2∼5). The RF frequency is 40 MHz and the toroidal field is 2 kG, which corresponds to ω = 13ωcH. The experiment is conducted in the density range n̄e ∼ 2 × 1018 m−3 where only the fast wave can propagate, eliminating the possibility of slow wave current drive. This density is two orders of magnitude higher than the density limit predicted for slow wave current drive. The dependence of the drive efficiency on the relative phase difference Δφ is clearly observed with a maximum of about Δφ = π/4. The plasma current was limited by MHD instability which begins to occur around qa = 10.

Current drive by fast magnetosonic waves is successfully performed in the JIPP T-IIU tokamak by means of a four-element dipole antenna array with a Faraday shield. A plasma current of about 50 kA is sustained by an rf power of about 80 kW in a low-density plasma (3 x 10 12 cm" 3 ) with an efficiency comparable to that of slow-wave current drive. A density limit for fast magnetosonic current drive is observed, contrary to theoretical expectations based on linear wave propagation.PACS numbers: 52.35.Hr, 52.40.Db, 52.55.Fa Though extensive studies of sustainment, rampup, and startup of plasma current by slow waves in the lower hybrid (LH) frequency range have been conducted successfully, 1 "" 9 it has been clearly indicated that there exists a density limit beyond which current cannot be driven by the slow wave. 10 The profile of current driven by the slow waves tends to be hollow when applied to large tokamaks confining a hightemperature plasma. 11 Recently, current drive by fast waves has started to attract attention because the fast wave may drive the plasma current even in hightemperature and high-density plasmas where the slow wave is not feasible. 12 The main reason lies in the different characteristics of the fast wave near the LH frequency: no mode conversion to electrostatic warm plasma wave and less absorption as a result of the weak Landau damping in the framework of linear theory. Nonlinear effects, which hinder the propagation of the fast wave to the high-density region, might be weakened because the electric field of fast waves is weak and no resonance cone exists for their propagation. 13 Because fast waves near the LH frequency with refractive indices N n~~0 (l) are mainly damped by electron Landau damping, tokamak plasmas with electron temperatures higher than several kiloelectronvolts, or with a fast electron tail, are imperative for greater efficiency in the current drive. Current drive by fast waves was studied experimentally in a low-temperature plasma by a few groups, and driven plasma currents of a few kiloamperes or less were observed. 14 " 17 In this Letter, we present the first successful experiment in a tokamak plasma of the "slide-away" regime 18,19 where a large current is sustained by fast waves near the LH frequency.The experiment was carried out in the JIPP T-IIU tokamak 20 with minor (major) radius a =0.25 m (#=0.93 m) at £, = 26.4 kG. A fast magnetosonic (FMS) wave at / 0 = 800 MHz (f 0 -20f cl )is launched into a hydrogen plasma in the slide-away regime from a four-element dipole antenna array, as shown in Fig. 1(a). Each dipole antenna, 2.0 cm in width and 19.6 cm in length, is separated from another by a distance of 3.6 cm. To prevent direct rf radiation in the toroidal direction the antenna system is housed in a FIG. 1. (a) Four-element dipole antenna array with Faraday shield; (b) rf voltage V r r picked up by a Hertz dipole located at the origin as a function of angle 0; (c) rf voltage K rf at the origin as a function of angle X; (d) rf field E y on the Faraday shield ...

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The coupling of ICRF power from a slow-wave antenna to a plasma with finite temperature is examined. A heuristic model, allowing explicit representations of ion Bernstein waves, fast waves and slow waves, is used to clarify how the antenna power is partitioned into the various wave energy fluxes. This model is complemented quantitatively by a more elaborate and realistic computer model. It is shown that such antennas can be highly efficient in transferring most of the antenna power directly to ion Bernstein waves, with only a very small fraction going into fast waves. The potentiality of this coupling scheme for plasma heating in ICRF is briefly discussed.

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