8,637 research outputs found
Dielectric responses of the layered cobalt oxysulfide Sr_2Cu_2CoO_2S_2 with CoO_2 square-planes
We have studied the dielectric responses of the layered cobalt oxysulfide
SrCuCoOS with the CoO square-planes. With decreasing
temperature below the N\'eel temperature, the resistivity increases like a
semiconductor, and the thermopower decreases like a metal. The dielectric
constant is highly dependent on temperature, and the dielectric relaxation is
systematically changed with temperature, which is strongly correlated to the
magnetic states. These behaviors suggest that carriers distributed
homogeneously in the paramagnetic state at high temperatures are expelled from
the antiferromagnetically ordered spin domain below the N\'eel temperature.Comment: 3 pages, 4 eps figures, to be published in J. Appl. Phy
Scanning Electron Microscopic Studies of the Oral Mucosa and Its Microvasculature: A Review of the Palatine Mucosa and Its Microvascular Architecture in Mammals
The present paper deals with the microvascular architecture of the palatine mucosa in primates, camivorae, and rodentia utilizing microvascular corrosion castings and epithelium-separated specimens.
The submucous vascular network is under-developed since the bard palatine mucosa was designated the mucoperiosteum, except some areas. The palatine venous plexus appears to show regional differences with animal species differences. The well-developed plexus is observed to be two-layered and may contribute to the process of regurgitation of rough food and assist in mastication with the palatine plicae. Formation and patterns of the arterial network in the lamina propria are in a close relation with connective tissue elements. The subepithelial capillary network constitutes an advanced base for the ascending crus of the capillary loop and its pattern is affected by the properties of the connective tissue papillae and the diverging fashion of the capillary loops.
Capillary loops of the transverse palatine plica are arranged parallel to the sagittal axis and at right angles to the top line of each plica. Features of the capillary loops are characteristics in the top, the anterior and posterior slopes of the plica, respectively. High connective tissue papillae in both the anterior slope and plical top may be of a resistant form for mollifying exhaustion, affected by the periodicity and mastication function. Although it is difficult to elucidate the lamination of the palatine mucosa in histological slides, it was resolved by examination on its vascular architectures
Electron-phonon interaction in the solid form of the smallest fullerene C
The electron-phonon coupling of a theoretically devised carbon phase made by
assembling the smallest fullerenes C is calculated from first
principles. The structure consists of C cages in an {\it fcc} lattice
interlinked by two bridging carbon atoms in the interstitial tetrahedral sites
({\it fcc}-C). The crystal is insulating but can be made metallic by
doping with interstitial alkali atoms. In the compound NaC the
calculated coupling constant is 0.28 eV, a value much larger
than in C, as expected from the larger curvature of C. On the
basis of the McMillan's formula, the calculated =1.12 and a
assumed in the range 0.3-0.1 a superconducting T in the range 15-55 K is
predicted.Comment: 7 page
A Solution for Little Hierarchy Problem and b --> s gamma
We show that all the parameters which destabilize the weak scale can be taken
around the weak scale in the MSSM without conflicting with the SM Higgs mass
bound set by LEP experiment. The essential point is that if the lightest
CP-even Higgs h in the MSSM has only a small coupling to Z boson, g_{ZZh}, LEP
cannot generate the Higgs sufficiently. In the scenario, the SM Higgs mass
bound constrains the mass of the heaviest CP-even Higgs H which has the SM like
g_{ZZH} coupling. However, it is easier to make the heaviest Higgs heavy by the
effect of off-diagonal elements of the mass matrix of the CP-even Higgs because
the larger eigenvalue of 2 times 2 matrix becomes larger by introducing
off-diagonal elements. Thus, the smaller stop masses can be consistent with the
LEP constraints. Moreover, the two excesses observed at LEP Higgs search can
naturally be explained as the signals of the MSSM Higgs h and H in this
scenario. One of the most interesting results in the scenario is that all the
Higgs in the MSSM have the weak scale masses. For example, the charged Higgs
mass should be around 130 GeV. This looks inconsistent with the lower bound
obtained by the b --> s gamma process as m_{H^\pm}>350GeV. However, we show
that the amplitude induced by the charged Higgs can naturally be compensated by
that of the chargino if we take the mass parameters by which the little
hierarchy problem can be solved. The point is that the both amplitudes have the
same order of magnitudes when all the fields in the both loops have the same
order of masses.Comment: 14 pages, 5 figures, input parameter slightly changed, figures
replaced, references correcte
Pulse-coupled resonate-and-fire models
We analyze two pulse-coupled resonate-and-fire neurons. Numerical simulation
reveals that an anti-phase state is an attractor of this model. We can
analytically explain the stability of anti-phase states by means of a return
map of firing times, which we propose in this paper. The resultant stability
condition turns out to be quite simple. The phase diagram based on our theory
shows that there are two types of anti-phase states. One of these cannot be
seen in coupled integrate-and-fire models and is peculiar to resonate-and-fire
models. The results of our theory coincide with those of numerical simulations.Comment: 15 pages, 8 figure
Anomalous He-Gas High-Pressure Studies on Superconducting LaO1-xFxFeAs
AC susceptibility measurements have been carried out on superconducting
LaO1-xFxFeAs for x=0.07 and 0.14 under He-gas pressures to about 0.8 GPa. Not
only do the measured values of dTc/dP differ substantially from those obtained
in previous studies using other pressure media, but the Tc(P) dependences
observed depend on the detailed pressure/temperature history of the sample. A
sizeable sensitivity of Tc(P) to shear stresses provides a possible
explanation
Synapse efficiency diverges due to synaptic pruning following over-growth
In the development of the brain, it is known that synapses are pruned
following over-growth. This pruning following over-growth seems to be a
universal phenomenon that occurs in almost all areas -- visual cortex, motor
area, association area, and so on. It has been shown numerically that the
synapse efficiency is increased by systematic deletion. We discuss the synapse
efficiency to evaluate the effect of pruning following over-growth, and
analytically show that the synapse efficiency diverges as O(log c) at the limit
where connecting rate c is extremely small. Under a fixed synapse number
criterion, the optimal connecting rate, which maximize memory performance,
exists.Comment: 15 pages, 16 figure
Thermodynamic Properties of the Piecewise Uniform String
The thermodynamic free energy F is calculated for a gas whose particles are
the quantum excitations of a piecewise uniform bosonic string. The string
consists of two parts of length L_I and L_II, endowed with different tensions
and mass densities, adjusted in such a way that the velocity of sound always
equals the velocity of light. The explicit calculation is done under the
restrictive condition that the tension ratio x = T_I/T_II approaches zero.
Also, the length ratio s = L_II/L_I is assumed to be an integer. The expression
for F is given on an integral form, in which s is present as a parameter. For
large values of s, the Hagedorn temperature becomes proportional to the square
root of s.Comment: 32 pages, latex, no figure
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