14,990 research outputs found
General Connectivity Distribution Functions for Growing Networks with Preferential Attachment of Fractional Power
We study the general connectivity distribution functions for growing networks
with preferential attachment of fractional power, ,
using the Simon's method. We first show that the heart of the previously known
methods of the rate equations for the connectivity distribution functions is
nothing but the Simon's method for word problem. Secondly, we show that the
case of fractional the -transformation of the rate equation
provides a fractional differential equation of new type, which coincides with
that for PA with linear power, when . We show that to solve such a
fractional differential equation we need define a transidental function
that we call {\it upsilon function}. Most of all
previously known results are obtained consistently in the frame work of a
unified theory.Comment: 10 page
Isoscalar monopole excitations in O: -cluster states at low energy and mean-field-type states at higher energy
Isoscalar monopole strength function in O up to MeV is
discussed. We found that the fine structures at the low energy region up to
MeV in the experimental monopole strength function obtained
by the O reaction can be rather satisfactorily
reproduced within the framework of the cluster model, while the gross
three bump structures observed at the higher energy region ( MeV) look likely to be approximately reconciled by the mean-field
calculations such as RPA and QRPA. In this paper, it is emphasized that two
different types of monopole excitations exist in O; one is the monopole
excitation to cluster states which is dominant in the lower energy part ( MeV), and the other is the monopole excitation of the mean-field
type such as one-particle one-hole () which {is attributed} mainly to the
higher energy part ( MeV). It is found that this
character of the monopole excitations originates from the fact that the ground
state of O with the dominant doubly closed shell structure has a duality
of the mean-field-type {as well as} -clustering {character}. This dual
nature of the ground state seems to be a common feature in light nuclei.Comment: 35 pages, 5 figure
Evolution of deformations in medium-mass nuclei
Evolution of quadrupole deformations in and shell nuclei with mass
A= 1856 is studied by using deformed Skyrme Hartree-Fock (HF) model with
pairing correlations. We point out that the quadrupole deformations of the
nuclei with the isospin T=0 and T=1 show strong mass number dependence as a
clear manifestation of dynamical evolution of deformation in nuclear many-body
systems. The competition between the deformation driving particle-vibration
coupling and the closed shell structure is shown in a systematic study of the
ratios between the proton and neutron deformations in nuclei with
T=T=1. Calculated quadrupole and hexadecapole deformations are compared
with shell model results and available experimental data. A relation between
the skin thickness and the intrinsic Q moments is also discussed.Comment: 26 pages, 8figure
Nearly Instantaneous Alternatives in Quantum Mechanics
Usual quantum mechanics predicts probabilities for the outcomes of
measurements carried out at definite moments of time. However, realistic
measurements do not take place in an instant, but are extended over a period of
time. The assumption of instantaneous alternatives in usual quantum mechanics
is an approximation whose validity can be investigated in the generalized
quantum mechanics of closed systems in which probabilities are predicted for
spacetime alternatives that extend over time. In this paper we investigate how
alternatives extended over time reduce to the usual instantaneous alternatives
in a simple model in non-relativistic quantum mechanics. Specifically, we show
how the decoherence of a particular set of spacetime alternatives becomes
automatic as the time over which they extend approaches zero and estimate how
large this time can be before the interference between the alternatives becomes
non-negligible. These results suggest that the time scale over which coarse
grainings of such quantities as the center of mass position of a massive body
may be extended in time before producing significant interference is much
longer than characteristic dynamical time scales.Comment: 12 pages, harvmac, no figure
Incommensurate spin correlations induced by magnetic Fe ions substituted into overdoped Bi1.75Pb0.35Sr1.90CuO6+z
Spin correlations in the overdoped region of Bi1.75Pb0.35Sr1.90CuO6+z have
been explored with Fe-doped single crystals characterized by neutron
scattering, muon-spin-rotation (muSR) spectroscopy, and magnetic susceptibility
measurements. Static incommensurate spin correlations induced by the Fe spins
are revealed by elastic neutron scattering. The resultant incommensurability
delta is unexpectedly large (~0.2 r.l.u.), as compared with delta ~ 1/8 in
overdoped superconductor La2-xSrxCuO4. Intriguingly, the large delta in this
overdoped region is close to the hole concentration p. This result is
reminiscent of the delta ~ p trend observed in underdoped La2-xSrxCuO4;
however, it is inconsistent with the saturation of delta in the latter compound
in the overdoped regime. While our findings in Fe-doped
Bi1.75Pb0.35Sr1.90CuO6+z support the commonality of incommensurate spin
correlations in high-Tc cuprate superconductors, they also suggest that the
magnetic response might be dominated by a distinct mechanism in the overdoped
region.Comment: 4 pages, 5 figures. Revision in introduction, discussion, and
conclusion
In vivo microdialysis reveals age-dependent decrease of brain interstitial fluid tau levels in P301S human tau transgenic mice
Although tau is a cytoplasmic protein, it is also found in brain extracellular fluids, e.g., CSF. Recent findings suggest that aggregated tau can be transferred between cells and extracellular tau aggregates might mediate spread of tau pathology. Despite these data, details of whether tau is normally released into the brain interstitial fluid (ISF), its concentration in ISF in relation to CSF, and whether ISF tau is influenced by its aggregation are unknown. To address these issues, we developed a microdialysis technique to analyze monomeric ISF tau levels within the hippocampus of awake, freely moving mice. We detected tau in ISF of wild-type mice, suggesting that tau is released in the absence of neurodegeneration. ISF tau was significantly higher than CSF tau and their concentrations were not significantly correlated. Using P301S human tau transgenic mice (P301S tg mice), we found that ISF tau is fivefold higher than endogenous murine tau, consistent with its elevated levels of expression. However, following the onset of tau aggregation, monomeric ISF tau decreased markedly. Biochemical analysis demonstrated that soluble tau in brain homogenates decreased along with the deposition of insoluble tau. Tau fibrils injected into the hippocampus decreased ISF tau, suggesting that extracellular tau is in equilibrium with extracellular or intracellular tau aggregates. This technique should facilitate further studies of tau secretion, spread of tau pathology, the effects of different disease states on ISF tau, and the efficacy of experimental treatments
Direct relation between the low-energy spin excitations and superconductivity of overdoped high- superconductors
The dynamic spin susceptibility, , has been measured over the
energy range of meV for overdoped
LaSrCuO. Incommensurate (IC) spin excitations are observed
at 8 K for all superconducting samples for with
peaking at meV. The IC peaks at 6 meV become smaller in
intensity with increasing and, finally, become unobservable for a sample
with which has no bulk superconductivity. The maximum
decreases linearly with (onset) in the overdoped region, implying a direct
cooperative relation between the spin fluctuations and the superconductivity.Comment: 4 pages, 4 figure
- …