8,991 research outputs found
Unbinding Transition Induced by Osmotic Pressure in Relation to Unilamellar Vesicle Formation
Small-angle X-ray scattering and phase-contrast microscopy experiments were
performed to investigate the effect of the osmotic pressure on vesicle
formation in a dioleoylphosphatidylcholine (DOPC)/water/NaI system.
Multi-lamellar vesicles were formed when a pure lipid film was hydrated with an
aqueous solution of NaI. On the other hand, uni-lamellar vesicles (ULVs) were
formed when a lipid film mixed with an enough amount of NaI was hydrated. To
confirm the effect of the osmotic pressure due to NaI, a free-energy
calculation was performed. This result showed that the osmotic pressure induced
an unbinding transition on the hydration process, which resulted in ULV
formation
Orbital Properties of Sr3Ru2O7 and Related Ruthenates Probed by 17O-NMR
We report a site-separated O-NMR study of the layered perovskite
ruthenate SrRuO, which exhibits nearly two-dimensional transport
properties and itinerant metamagnetism at low temperatures. The local hole
occupancies and the spin densities in the oxygen orbitals are obtained by
means of tight-binding analyses of electric field gradients and anisotropic
Knight shifts. These quantities are compared with two other layered perovskite
ruthenates: the two-dimensional paramagnet SrRuO and the
three-dimensional ferromagnet SrRuO. The hole occupancies at the oxygen
sites are very large, about one hole per ruthenium atom. This is due to the
strong covalent character of the Ru-O bonding in this compound. The magnitude
of the hole occupancy might be related to the rotation or tilt of the RuO
octahedra. The spin densities at the oxygen sites are also large, 20-40% of the
bulk susceptibilities, but in contrast to the hole occupancies, the spin
densities strongly depend on the dimensionality. This result suggests that the
density-of-states at the oxygen sites plays an essential role for the
understanding of the complex magnetism found in the layered perovskite
ruthenates.Comment: 9 pages, 5 figures, to be published in Phys. Rev.
Angle-Resolved Photoemission Spectroscopy of the Antiferromagnetic Superconductor Nd1.87Ce0.13CuO4: Anisotropic Spin-Correlation Gap, Pseudogap, and the Induced Quasiparticle Mass Enhancement
We performed high-resolution angle-resolved photoemission spectroscopy on
Nd1.87Ce0.13CuO4, which is located at the boundary of the antiferromagnetic
(AF) and the superconducting phase. We observed that the quasiparticle (QP)
effective mass around (pi, 0) is strongly enhanced due to the opening of the AF
gap. The QP mass and the AF gap are found to be anisotropic, with the largest
value near the intersecting point of the Fermi surface and the AF zone
boundary. In addition, we observed that the QP peak disappears around the Neel
temperature (TN) while the AF pseudogap is gradually filled up at much higher
temperatures, possibly due to the short-range AF correlation.Comment: 4 pages, 4 figure
Large-Area Scintillator Hodoscope with 50 ps Timing Resolution Onboard BESS
We describe the design and performance of a large-area scintillator hodoscope
onboard the BESS rigidity spectrometer; an instrument with an acceptance of 0.3
m^{2}sr.
The hodoscope is configured such that 10 and 12 counters are respectively
situated in upper and lower layers.
Each counter is viewed from its ends by 2.5 inch fine-mesh photomultiplier
tubes placed in a stray magnetic field of 0.2 Tesla.
Various beam-test data are presented.
Use of cosmic-ray muons at ground-level confirmed 50 ps timing resolution for
each layer, giving an overall time-of-flight resolution of 70 ps rms using a
pure Gaussian resolution function.
Comparison with previous measurements on a similar scintillator hodoscope
indicates good agreement with the scaling law that timing resolution is
proportional to 1/, where is the effective
number of photoelectrons.Comment: 16 pages, 14 figure
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