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Attempts were made to isolate endophytic Frankia from the root nodules formed on Casuarina equisetifolia grown in a mixture of vermiculite and field soil obtained from the Okayama University Campus. The isolation of Frankia was performed by macerating a nodule lobe directly in a test tube containing modified Qmod medium with casamino acids and sodium pyruvate as nitrogen and carbon sources. One colony, which showed hyphal and sporangial characteristics similar to those of Frankia, appeared in a test tube after 1-month incubation. The root nodules were successfully formed on the roots of the host plants by inoculation of the isolate which was multiplied using the original Qmod medium containing yeast extract, peptone and propionate. The acetylene reduction activity (ARA) obtained was 6.29 ± 1.57 µmol C2H4 h−1 (g F.W. nod.)−1. Accordingly, we identified the isolate as an effective Frankia strain for C. equisetifolia and designated it as Ceq1. Since this strain also formed root nodules on Alnus sieb...

The two-dimensional magnetohydrodynamic flow is investigated, in which the applied magnetic field is produced by an electric current perpendicular to the main flow whose speed is supersonic. The equations are linearlized assuming that the magnetic Reynolds number and the interaction parameter are small, and the solutions are obtained by means of the bilateral Laplace transform. The numerical results show that the flow is decelerated almost over the flow region, and that downstream of the current position remarkably oscillatory variations occur in the retarded flow. These features of supersonic flow are particularly of interest as compared with the subsonic case.

The axisymmetric steady flow of an infinite or cylindrically bounded, inviscid, compressible fluid is investigated assuming that the magnetic Reynolds number and the interaction parameter are small. For the unbounded flow the radial velocity alone is evaluated with reference to the potential theory. For the channel flow, the solutions are obtained using the finite Hankel transform and they consist of two parts, namely, the convolution integral term and the magnetic field integral term. In the subsonic case, the first term is negligible because of its exponential damping so that the flow field is explicitly determined by the magnetic field applied. In the supersonic case, the first term is rather dominant and periodic so that the flow field remains oscillatory to infinity downstream. This oscillatory behavior results from the existence of discontinuity (Mach cones or lines) continuing by reflection off the wall of the cylinder.

The transient supersonic flow of a slightly conducting gas in an MHD channel with axial symmetry is investigated assuming that the magnetic Reynolds number and the interaction parameter are small. The solutions to the linearized equations for supersonic flow show that in the asymptotic limit as t →∞, these solutions all tend to coincide with the solutions for the corresponding steady flow. This point is remarkably different as compared with the result for the transient subsonic flow in a channel. The reason for this discrepancy is made clear. The time for the transient flow to achieve the steady state is also evaluated.