9,033 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
HEAT repeats – versatile arrays of amphiphilic helices working in crowded environments?
Cellular proteins do not work alone in diluted conditions. They often function as part of large macromolecular complexes, which are transported and concentrated into specific cellular compartments and function in their highly crowded environments. A central theme of modern cell biology is to understand how cellular proteins might achieve these challenging tasks efficiently and faithfully. In this Opinion article, we will focus on HEAT repeats, flexible arrays of amphiphilic helices found in many eukaryotic proteins such as karyopherins and condensins, and discuss how this uniquely designed helical repeats might underlie dynamic protein-protein interactions and support cellular functions in crowded environments. We will make bold speculations on functional similarities between HEAT repeats and intrinsically disordered regions (IDRs) in macromolecular phase separation. Potential contributions of HEAT-HEAT interactions, as well as cooperation between HEATs and IDRs, to mesoscale organelle assembly will be discussed
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