1,646 research outputs found
Dynamics of Binary Mixtures with Ions: Dynamic Structure Factor and Mesophase Formation
Dynamic equations are presented for polar binary mixtures containing ions in
the presence of the preferential solvation. In one-phase states, we calculate
the dynamic structure factor of the composition accounting for the ion motions.
Microphase separation can take place for sufficiently large solvation asymmetry
of the cations and the anions. We show two-dimensional simulation results of
the mesophase formation with an antagonistic salt, where the cations are
hydrophilic and the anions are hydrophobic. The structure factor S(q) in the
resultant mesophase has a sharp peak at an intermediate wave number on the
order of the Debye-Huckel wave number. As the quench depth is increased, the
surface tension nearly vanishes in mesophases due to an electric double layer.Comment: 24 pages, 10 figures, to appear in Journal of Physics: Condensed
Matte
Magnetic properties of PrCu at high pressure
We report a study of the low-temperature high-pressure phase diagram of the
intermetallic compound PrCu, by means of molecular-field calculations and
Cu nuclear-quadrupole-resonance (NQR) measurements under pressure.
The pressure-induced magnetically-ordered phase can be accounted for by
considering the influence of the crystal electric field on the electron
orbitals of the Pr ions and by introducing a pressure-dependent exchange
interaction between the corresponding local magnetic moments. Our experimental
data suggest that the order in the induced antiferromagnetic phase is
incommensurate. The role of magnetic fluctuations both at high and low
pressures is also discussed.Comment: 7 pages, 6 figures, submitted to Eur. Phys. J.
Spatio-Temporal and Multisensory Integration: the relationship between sleep and the cerebellum
Does the cerebellum sleep? If so, does sleep contribute to cerebellar cognition? In this thesis, the sleep contribution to the consolidation process of spatial-temporal and multisensory integration was investigated in relation to the human cerebellum. Multiple experimental approaches were used to answer research questions addressed in the various chapters. Summarizing the evidence of the electrophysiology and neuroimaging studies, in Chapter1 we present intriguing evidence that the cerebellum is involved in sleep physiology, and that cerebellar-dependent memory formation can be consolidated during sleep. In Chapter 2, using functional neuroimaging in healthy participants during various forms of the Serial interception sequential learning (SISL) task, i.e., predictive timing, motor coordination, and motor imagination, we assessed the cerebellar involvement in spatio-temporal predictive timing; and possible cerebellar interactions with other regions, most notably the hippocampus. In Chapter 3, we add to the findings of Chapter 2 that indicate the cerebellum and hippocampus are involved in the task, by showing that more than simply activated, the cerebellum is a necessary and responsible region for the establishment of the spatio-temporal prediction. This follows from the deficits in behavioral properties of the predictive and reactive timing in the cerebellar ataxia type 6 patients, using the modified version of the SISL task. In Chapter 4, we assessed the subsequent post-interval behavioral performances on the learning of the fixed and random timing sequences in the SISL task, comparing a sleep group and wake group in healthy participants. Our findings show that sleep consolidates the process of cerebellar-dependent spatio-temporal integration. In Chapter 5, we investigated the establishment of visual-tactile integration during sleep through the examination of tactile motion stimulation during sleep and showed that, subsequent to sleep, directional visual motion discrimination i
Strong Coupling between Antiferromagnetic and Superconducting Order Parameters in CeRhIn Studied by In-NQR Spectroscopy
We report on a novel pressure ()-induced evolution of magnetism and
superconductivity (SC) in a helical magnet CeRhIn with an incommensurate
wave vector through the In nuclear quadrupole
resonance (NQR) measurements under . Systematic measurements of the
In-NQR spectrum reveal that the commensurate antiferromagnetism (AFM)
with is realized above 1.7 GPa. An
important finding is that the size of SC gap and increase as the
magnitude of the AFM moment decreases in the region, where SC uniformly
coexists with the commensurate AFM. This result provides evidence of strong
coupling between the commensurate AFM order parameter (OP) and SC OP.Comment: 5 pages, 5 figure
Anomalous quasiparticle transport in the superconducting state of CeCoIn5
We report on a study of thermal Hall conductivity k_xy in the superconducting
state of CeCoIn_5. The scaling relation and the density of states of the
delocalized quasiparticles, both obtained from k_xy, are consistent with d-wave
superconducting symmetry. The onset of superconductivity is accompanied by a
steep increase in the thermal Hall angle, pointing to a striking enhancement in
the quasiparticle mean free path. This enhancement is drastically suppressed in
a very weak magnetic field. These results highlight that CeCoIn_5 is unique
among superconductors. A small Fermi energy, a large superconducting gap, a
short coherence length, and a long mean free path all indicate that CeCoIn_5 is
clearly in the superclean regime (E_F/Delta<<l/xi), in which peculiar vortex
state is expected.Comment: 5 pages, 5 figure
Superconducting Gap Function in Antiferromagnetic Heavy-Fermion UPd_2Al_3 Probed by Angle Resolved Magnetothermal Transport Measurements
The superconducting gap structure of heavy fermion UPd_2Al_3, in which
unconventional superconductivity coexists with antiferromagnetic (AF) order
with atomic size local moments, was investigated by the thermal conductivity
measurements in a magnetic field rotating in various directions relative to the
crystal axes. The results provide strong evidence that the gap function
\Delta(k) has a single line node orthogonal to the c-axis located at the AF
Brillouin zone boundary, while \Delta(k) is isotropic within the basal plane.
The determined nodal structure is compatible with the resonance peak in the
dynamical susceptibility observed in neutron inelastic scattering experiments.
Based on these results, we conclude that the superconducting pairing function
of UPd_2Al_3 is most likely to be d-wave with a form \Delta(k)=\Delta_0
cos(k_zc)Comment: 10 pages, 9 figure
Phase separation transition in liquids and polymers induced by electric field gradients
Spatially uniform electric fields have been used to induce instabilities in
liquids and polymers, and to orient and deform ordered phases of
block-copolymers. Here we discuss the demixing phase transition occurring in
liquid mixtures when they are subject to spatially nonuniform fields. Above the
critical value of potential, a phase-separation transition occurs, and two
coexisting phases appear separated by a sharp interface. Analytical and
numerical composition profiles are given, and the interface location as a
function of charge or voltage is found. The possible influence of demixing on
the stability of suspensions and on inter-colloid interaction is discussed.Comment: 7 pages, 3 figures. Special issue of the J. Phys. Soc. Ja
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