836 research outputs found
Dynamical frictional phenomena in an incommensurate two-chain model
Dynamical frictional phenomena are studied theoretically in a two-chain model
with incommensurate structure. A perturbation theory with respect to the
interchain interaction reveals the contributions from phonons excited in each
chain to the kinetic frictional force. The validity of the theory is verified
in the case of weak interaction by comparing with numerical simulation. The
velocity and the interchain interaction dependences of the lattice structure
are also investigated. It is shown that peculiar breaking of analyticity states
appear, which is characteristic to the two-chain model. The range of the
parameters in which the two-chain model is reduced to the Frenkel-Kontorova
model is also discussed.Comment: RevTex, 9 pages, 7 PostScript figures, to appear in Phys. Rev.
Effect of Local Inhomogeneity on Nucleation; Case of Charge Density Wave Depinning
The spatial inhomogeneities are expected to affect nucleation process in an
essential way. These effects are studied theoretically by considering the case
of the depinning of the charge density wave as a typical example. The threshold
field of the depinning of the one-dimensional commensurate charge density wave
with one impurity has been examined classically based on the phase Hamiltonian
at absolute zero. It is found that the threshold field is lowered by a finite
amount compared to that in the absence of an impurity.Comment: pages 12, LaTeX, 9 figures, uses jpsj.sty, submitted to J. Phys. Soc.
Jp
Crossover from 2-dimensional to 1-dimensional collective pinning in NbSe3
We have fabricated NbSe structures with widths comparable to the
Fukuyama-Lee-Rice phase-coherence length. For samples already in the
2-dimensional pinning limit, we observe a crossover from 2-dimensional to
1-dimensional collective pinning when the crystal width is less than 1.6
m, corresponding to the phase-coherence length in this direction. Our
results show that surface pinning is negligible in our samples, and provide a
means to probe the dynamics of single domains giving access to a new regime in
charge-density wave physics.Comment: 4 pages, 2 figures, and 1 table. Accepted for publication in Physical
Review
Superconductivity of the One-Dimensional d-p Model with p-p transfer
Using the numerical diagonalization method, we investigate the
one-dimensional - model, simulating a Cu-O linear chain with strong
Coulomb repulsions. Paying attention to the effect of the transfer energy
between the nearest neighbor oxygen-sites, we calculate the critical
exponent of correlation functions based on the Luttinger liquid
relations and the ground state energy as a function of an external
flux . We find that the transfer increases the charge
susceptibility and the exponent in cooperation with the repulsion
at Cu-site. We also show that anomalous flux quantization occurs for
. The superconducting region is presented on a phase diagram of
vs. plane.Comment: 4 pages, RevTex + 5 PS figures include
Multiple diffusion pathways in LixNi0.77Co0.14Al0.09O2 (NCA) Li-ion battery cathodes
Experimental evidence for the presence of two computationally theorised diffusion pathways, namely the oxygen dumbbell hop (ODH) and tetrahedral site hop (TSH), has been given for the first time by muon spin relaxation (µSR) on sub-stoichiometric LixNi0.77Co0.14Al0.09O2. µSR has proven to be a powerful tool that is able to discriminate between diffusion pathways that occur on different timescales on a local level, where bulk electrochemical techniques cannot. Whereas the estimated values of DLi at lithium concentrations of 0.87 and 0.71 were found to be on the order of 10-11 by electrochemical impedance spectroscopy, contributions to diffusion from ODH and TSH were determined to be on the order of 10-11 and 10-10 cm2 s-1, and a factor of four decrease in Ea for both samples, in excellent agreement with theoretical calculations on related compounds. Rietveld refinement of both X-ray and neutron diffraction data was also used to interrogate the local structure of the materials where no contribution from Li+/Ni2+ cation mixing was observed
Whole genome integrity and enhanced developmental potential in ram freeze-dried spermatozoa at mild sub-zero temperature
Freeze-dried spermatozoa typically shows a reduction in fertility primarily due to the DNA damage resulting from the sublimation process. In order to minimize the physical/mechanical damage resulting from lyophilization, here we focused on the freezing phase, comparing two cooling protocols: (i) rapid-freezing, where ram sperm sample is directly plunged into liquid nitrogen (LN-group), as currently done; (ii) slow-freezing, where the sample is progressively cooled to − 50 °C (SF-group). The spermatozoa dried in both conditions were analysed to assess residual water content by Thermal Gravimetric Analysis (TGA) and DNA integrity using Sperm Chromatin Structure Assay (SCSA). TGA revealed more than 90% of water subtraction in both groups. A minor DNA damage, Double-Strand Break (DSB) in particular, characterized by a lower degree of abnormal chromatin structure (Alpha-T), was detected in the SF-group, comparing to the LN-one. In accordance with the structural and DNA integrity data, spermatozoa from SF-group had the best embryonic development rates, comparing to LN-group: cleaved embryos [42/100 (42%) versus 19/75 (25.3%), P < 0.05, SL and LN respectively] and blastocyst formation [7/100 (7%) versus 2/75 (2.7%), P < 0.05, SF and LN respectively]. This data represents a significant technological advancement for the development of lyophilization as a valuable and cheaper alternative to deep-freezing in LN for ram semen
Cortical Bone Trajectory Screw Placement Accuracy with a Patient-Matched 3-Dimensional Printed Guide in Lumbar Spinal Surgery: A Clinical Study
Development of Digital Based Millimeter Wave Interferometer and Application to Electron Density Imaging at the Potential Barrier Region on GAMMA10
Electronic States and Superconducting Transition Temperature based on the Tomonaga-Luttinger liquid in PrBaCuO
An NQR experiment revealed superconductivity of
PrBaCuO (Pr247) to be realized on CuO double chain
layers and suggests possibility of novel one-dimensional(1D) superconductivity.
To clarify the nature of the 1D superconductivity, we calculate the band
dispersions of Pr247 by using the generalized gradient approximation(GGA). It
indicates that Fermi surface of CuO double chains is well described to the
electronic structure of a quasi-1D system.
Assuming the zigzag Hubbard chain model to be an effective model of the
system, we derive tight binding parameters of the model from a fit to the
result of GGA. Based on the Tomonaga-Luttinger liquid theory, we estimate
transition temperature () of the quasi-1D zigzag Hubbard model from the
calculated value of the Luttinger liquid parameter . The result of
is consistent with that of experiments in Pr247 and it suggests that the
mechanism of the superconductivity is well understood within the concept of the
Tomonaga-Luttinger liquid.Comment: 4 pages, 5 figure
Angle-resolved photoemission in high Tc cuprates from theoretical viewpoints
The angle-resolved photoemission (ARPES) technique has been developed rapidly
over the last decay, accompanied by the improvement of energy and momentum
resolutions. This technique has been established as the most powerful tool to
investigate the high Tc cuprate superconductors. We review recent ARPES data on
the cuprates from a theoretical point of view, with emphasis on the systematic
evolution of the spectral weight near the momentum (pi,0) from insulator to
overdoped systems. The effects of charge stripes on the ARPES spectra are also
reviewed. Some recent experimental and theoretical efforts to understand the
superconducting state and the pseudogap phenomenon are discussed.Comment: Review, 25 pages, with 22 GIF figures. To appear in Supercond. Sci.
Technol. Vol. 13 April 2000. A version including PS figures can be found at
http://www.maekawa-lab.imr.tohoku.ac.jp/TOHYAMA/tohyama.ps.g
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