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We could consistently identify cord insertion and velamentous cord insertion with color Doppler imaging during routine sonography in the mid-trimester. Transvaginal color Doppler imaging and serial scans were needed to identify vasa previa.

We have investigated the magnetic structure of an insulating lightly doped La 1Ϫx Sr x MnO 3 with xϭ0.04,0.125, and 0.17 with neutron scattering technique and bulk magnetization measurements. The magnetic structure of the xϭ0.04 sample at 5 K is a commensurate layer-type (A-type͒ antiferromagnetism with the propagation vector ͓010͔ and the moment of 3.7Ϯ0.2 B /M n, being parallel to the ͓100͔ axis in the orthorhombic Pnma symmetry. In addition, a spontaneous magnetization of 0.28Ϯ0.02 B /M n is observed at 8 K by magnetization measurement. By contrast, the xϭ0.125 sample exhibits a large ferromagnetic moment of 3.7Ϯ0.2 B /Mn and a small A-type antiferromagnetic component of 0.23Ϯ0.1 B /M n, while the xϭ0.17 sample exhibits only a ferromagnetic component of 3.6Ϯ0.2 B /Mn. These results are consistent with a spin structure derived from the conventional double exchange mechanism, but rule out the possibility of a recently suggested spiral spin structure for the insulating La 1Ϫx Sr x MnO 3 system.Distorted perovskite manganese oxides such as La 1Ϫx Sr x MnO 3 and La 1Ϫx Ca x MnO 3 transform from an antiferromagnetic insulator to a ferromagnetic metal as substitution of La ions by alkaline-earth ions. 1-4 Such behavior has been long known as metallic transport phenomena mediated by a double exchange mechanism. 5-7 The recent discovery of a gigantic magnetoresistance, 8-15 lattice-structure switching by an external field 16 as well as field-induced insulator-metal transitions 17-19 has renewed interest in these perovskite-type manganese oxide systems. Manganese ions in the parent material LaMnO 3 have a 3d 4 configuration where three electrons occupy the t 2g orbitals, while one electron occupies the e g orbital. The number of e g electrons in LaMnO 3 corresponds to half filling, and makes the parent LaMnO 3 a Motttype antiferromagnetic insulator. The substitution of La ions by divalent ions leads to doping of holes to the e g orbitals, introducing an itinerant character as well as ferromagnetism to well-doped samples. For a lightly doped insulating regime of the solid solution system La 1Ϫx Sr x MnO 3 , however, the double exchange model suggests a canted antiferromagnetism as the magnetic structure. 7 On the other hand, based on a mean field treatment of localized t 2g electrons and itinerant e g electrons with a strong Hund coupling, Inoue and Maekawa 20 recently proposed that a spiral state can be energetically more favorable than a canted antiferromagnetic state for a nearly half-doped insulating regime. This theory suggests that the spiral state continuously changes to the ferromagnetic state as a function of hole doping from half filling.In a pioneering work by Wollan and Koehler in 1955, the magnetic structures of the LaMnO 3ϩ␦ system as well as the La 1Ϫx Ca x MnO 3 system were studied by the neutron diffraction technique. 2 The spin structure of the LaMnO 3ϩ␦ system was reported to be a canted antiferromagnet where a layer type ͑a so-called A-type͒ antiferromagnetic ͑AF͒ structure coexists with a ferromagnet...

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Inelastic neutron scattering measurements were performed on large volume ͑ϳ2 cm 3 ͒ single crystals of 11 B substituted intermetallic superconductor YNi 2 11 B 2 C. With decreasing temperature, a gradual softening of a phonon spectrum is observed at around Q ͑0.525, 0, 8͒, similar to the case of LuNi 2 B 2 C reported by Dervenagas et al. [Phys. Rev. B 52, R9839 (1995)]. In addition, we discovered that an intense new peak appears below T c 14.2 K. With application of magnetic field, however, it is easily suppressed and disappears by H H c2 (ϳ4.7 T at T 5.5 K). These results strongly indicate that this new peak is undoubtedly associated with its superconducting state. [S0031-9007(96)