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We report Cu NQR results on Ge-doped heavy-fermion superconductors CeCu 2 (Si 1Ϫx Ge x ) 2 (0Ͻxр0.2) and compare with previous results on Ce 0.99 Cu 2.02 Si 2 (xϭ0). Once only 1% Ge is substituted for Si to expand the lattice, an antiferromagnetic ͑AFM͒ order sets in at T N ϳ0.7 K, followed by the onset of superconductivity at T c ϭ0.5 K. The sudden emergence of AFM order due to the slight Ge doping reinforces that an exotic magnetic phase at xϭ0 is in fact a marginal AFM state where slowly fluctuating AFM waves propagate over a long distance. The appearance of internal fields throughout the sample that is deduced from the NQR spectral shape below T N , excludes the presence of phase segregation between the superconducting ͑SC͒ and the AFM phases in the coexistent state below T c . The 1/T 1 result does not show significant reduction below T c , followed by a T 1 Tϭconst behavior. This indicates that the SC phase is in a gapless regime, dominated by magnetic excitations due to the coexistence of AFM and SC phase. As Ge content increases, T N is progressively increased, while T c is steeply decreased. As a result of the suppression of the slowly fluctuating AFM waves in the samples with more than xϭ0.06, their magnetic properties above T N progressively change to those in a localized regime as observed in CeCu 2 Ge 2 . The exotic interplay between magnetism and superconductivity in 0рxϽ0.06 is discussed in the context of a SO͑5͒ theory that unifies superconductivity and antiferromagnetism.

We have fabricated a simple Si-MEMS device consisting of a microcantilever and a base to measure active tension generated by skeletal muscle myotubes derived from murine myoblast cell line C2C12. We have developed a fabrication process for integration of myotubes onto the device. To position myotubes over the gap between the cantilever and the base without damage due to mechanical peeling or the use of an enzymatic reaction, we cultured myotubes on poly-N-isopropylacrylamide (PNIPAAm) as a sacrifice layer. By means of immune staining of alpha-actinin, it was confirmed that a myotube micropatterned onto the device bridged the gap between the cantilever and the base. After 7d differentiation, the myotube was actuated by electrical stimulation. The active tension generated by the myotube was evaluated by measuring the bending of the cantilever using image processing. On twitch stimulation, the myotube on the device contracted and generated active tension in response to the electrical signals. On tetanus tension measurement, approximately 1.0 microN per single myotube was obtained. The device developed here can be used in wide area of in vitro skeletal muscle studies, such as drug screening, physiology, regenerative medicine, etc.

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