260 research outputs found
Differences in Obstetric Care Between Japan and the US: A Qualitative Analysis of Blogs
Aim
To investigate patient-reported differences in obstetric care between Japan and the US by characterizing the information Japanese immigrants and expatriates share online
Influence of brain-derived neurotrophic factor on pathfinding of dentate granule cell axons, the hippocampal mossy fibers
Mossy fibers, the dentate granule cell axons, are generated throughout an animal's lifetime. Mossy fiber paths and synapses are primarily restricted to the stratum lucidum within the CA3 region. Brain-derived neurotrophic factor (BDNF), a neurotrophin family protein that activates Trk neurotrophin receptors, is highly expressed in the stratum lucidum in an activity-dependent manner. The addition of a Trk neurotrophin receptor inhibitor, K252a, to cultured hippocampal slices induced aberrant extension of mossy fibers into ectopic regions. BDNF overexpression in granule cells ameliorated the mossy fiber pathway abnormalities caused by a submaximal dose of K252a. A similar rescue was observed when BDNF was expressed in CA3 pyramidal cells, most notably in mossy fibers distal to the expression site. These findings are the first to clarify the role of BDNF in mossy fiber pathfinding, not as an attractant cue but as a regulator, possibly acting in a paracrine manner. This effect of BDNF may be as a signal for new fibers to fasciculate and extend further to form synapses with neurons that are far from active BDNF-expressing synapses. This mechanism would ensure the emergence of new independent dentate gyrus-CA3 circuits by the axons of new-born granule cells
Spin-density-wave transition of (TMTSF)PF at high magnetic fields
The transverse magnetoresistance of the Bechgaard salt (TMTSF)PF has
been measured for various pressures, with the field up to 24 T parallel to the
lowest conductivity direction c. A quadratic behavior is observed in
the magnetic field dependence of the spin-density-wave (SDW) transition
temperature . With increasing pressure,
decreases and the coefficient of the quadratic term increases. These results
are consistent with the prediction of the mean-field theory based on the
nesting of the quasi one-dimensional Fermi surface. Using a mean field theory,
for the perfect nesting case is estimated as about 16 K. This
means that even at ambient pressure where is 12 K, the SDW
phase of (TMTSF)PF is substantially suppressed by the
two-dimensionality of the system.Comment: 11pages,6figures(EPS), accepted for publication in PR
SDW and FISDW transition of (TMTSF)ClO at high magnetic fields
The magnetic field dependence of the SDW transition in (TMTSF)ClO for
various anion cooling rates has been measured, with the field up to 27T
parallel to the lowest conductivity direction . For quenched
(TMTSF)ClO, the SDW transition temperature increases
from 4.5K in zero field up to 8.4K at 27T. A quadratic behavior is observed
below 18T, followed by a saturation behavior. These results are consistent with
the prediction of the mean-field theory. From these behaviors,
is estimated as =13.5K for the perfect nesting case. This
indicates that the SDW phase in quenched (TMTSF)ClO, where is less than 6K, is strongly suppressed by the two-dimensionality of
the system. In the intermediate cooled state in which the SDW phase does not
appear in zero field, the transition temperature for the field-induced SDW
shows a quadratic behavior above 12T and there is no saturation behavior even
at 27T, in contrast to the FISDW phase in the relaxed state. This behavior can
probably be attributed to the difference of the dimerized gap due to anion
ordering.Comment: 4pages,5figures(EPS), accepted for publication in PR
Erroneous selection of a non-target item improves subsequent target identification in rapid serial visual presentations
The second of two targets (T2) embedded in a rapid serial visual presentation
(RSVSVP) is often missed even though the first (T1) is correctly reported
(attentional blink). The rate of correct T2 identification is quite high,
however, when T2 comes immediately after T1 (lag-1 sparing). This study
investigated whether and how non-target items induce lag-1 sparing. One T1 and
two T2s comprising letters were inserted in distractors comprising symbols in
each of two synchronised RSVSVPs. A digit (dummy) was presented with T1 in
another stream. Lag-1 sparing occurred even at the location where the dummy was
present (Experiment 1). This distractor-induced sparing effect was also obtained
even when a Japanese katakana character (Experiment 2) was used as the dummy.
The sparing effect was, however, severely weakened when symbols (Experiment 3)
and Hebrew letters (Experiment 4) served as the dummy. Our findings suggest a
tentative hypothesis that attentional set for item nameability is
meta-categorically created and adopted to the dummy only when the dummy is
nameable
Effect of Magnetic field on the Pseudogap Phenomena in High-Tc Cuprates
We theoretically investigate the effect of magnetic field on the pseudogap
phenomena in High-Tc cuprates.
The obtained results well explain the experimental results including their
doping dependences.
In our previous paper (J. Phys. Soc. Jpn. 68 (1999) 2999.), we have shown
that the pseudogap phenomena observed in High-Tc cuprates are naturally
understood as a precursor of the strong coupling superconductivity. On the
other hand, there is an interpretation for the recent high field NMR
measurements to be an evidence denying the pairing scenarios for the pseudogap.
In this paper, we investigate the magnetic field dependence of NMR
on the basis of our formalism and show the interpretation to be inappropriate.
The results indicate that the value of the characteristic magnetic field
is remarkably large in case of the strong coupling
superconductivity, especially near the pseudogap onset temperature .
Therefore, the magnetic field dependences can not be observed and does
not vary when the strong pseudogap anomaly is observed. On the other hand,
is small in the comparatively weak coupling case and
varies when the weak pseudogap phenomena are observed.
These results properly explain the high magnetic field NMR experiments
continuously from under-doped to over-doped cuprates.
Moreover, we discuss the transport phenomena in the pseudogap phase. The
behaviors of the in-plane resistivity, the Hall coefficient and the c-axis
resistivity in the pseudogap phase are naturally understood by considering the
d-wave pseudogap
New magnetic coherence effect in superconducting La_{2-x}Sr_{x}CuO_{4}
We have used inelastic neutron scattering to examine the magnetic
fluctuations at intermediate frequencies in the simplest high temperature
superconductor, La_{2-x}Sr_{x}Cu_{4}. The suppression of the low energy
magnetic response in the superconducting state is accompanied by an increase in
the response at higher energies. Just above a threshold energy of ~7 meV there
is additional scattering present below T_{c} which is characterised by an
extraordinarily long coherence length, in excess of 50 \AA.Comment: 11 pages, RevTeX, 4 postscript figure
Neutron Scattering Study of Spin Density Wave Order in the Superconducting State of Excess-Oxygen-Doped La2CuO4+y
We report neutron scattering measurements of spin density wave order within
the superconducting state of a single crystal of predominately stage-4
La2CuO4+y with a Tc(onset) of 42 K. The low temperature elastic magnetic
scattering is incommensurate with the lattice and is characterized by
long-range order in the copper-oxide plane with the spin direction identical to
that in the insulator. Between neighboring planes, the spins exhibit
short-range correlations with a stacking arrangement reminiscent of that in the
undoped antiferromagnetic insulator. The elastic magnetic peak intensity
appears at the same temperature within the errors as the superconductivity,
suggesting that the two phenomena are strongly correlated. These observations
directly reveal the persistent influence of the antiferromagnetic order as the
doping level increases from the insulator to the superconductor. In addition,
our results confirm that spin density wave order for incommensurabilities near
1/8 is a robust feature of the La2CuO4-based superconductors.Comment: 14 pages, LaTeX, includes 8 figure
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