4,687 research outputs found
Early and late stage profiles for a new chemotaxis model with density-dependent jump probability and quorum-sensing mechanisms
In this paper, we derive a new chemotaxis model with degenerate diffusion and
density-dependent chemotactic sensitivity, and we provide a more realistic
description of cell migration process for its early and late stages. Different
from the existing studies focusing on the case of non-degenerate diffusion, the
new model with degenerate diffusion causes us some essential difficulty on the
boundedness estimates and the propagation behavior of its compact support. In
the presence of logistic damping, for the early stage before tumour cells
spread to the whole body, we first estimate the expanding speed of tumour
region as for . Then, for the late stage of
cell migration, we further prove that the asymptotic profile of the original
system is just its corresponding steady state. The global convergence of the
original weak solution to the steady state with exponential rate
for some is also obtained
Confirming the 115.5-day periodicity in the X-ray light curve of ULX NGC 5408 X-1
The Swift/XRT light curve of the ultraluminous X-ray (ULX) source NGC 5408
X-1 was re-analyzed with two new numerical approaches, Weighted Wavelet
-transform (WWZ) and CLEANest, that are different from previous studies.
Both techniques detected a prominent periodicity with a time scale of
days, in excellent agreement with the detection of the same
periodicity first reported by Strohmayer (2009). Monte Carlo simulation was
employed to test the statisiticak confidence of the 115.5-day periodicity,
yielding a statistical significance of (or ). The robust
detection of the 115.5-day quasi-periodic oscillations (QPOs), if it is due to
the orbital motion of the binary, would infer a mass of a few thousand
for the central black hole, implying an intermediate-mass black hole
in NGC 5408 X-1.Comment: 6 pages, 2 figures, submitted to Research in Astronomy and
Astrophysics (RAA
Controlling the Intrinsic Josephson Junction Number in a Mesa
In fabricating intrinsic Josephson
junctions in 4-terminal mesa structures, we modify the conventional fabrication
process by markedly reducing the etching rates of argon ion milling. As a
result, the junction number in a stack can be controlled quite satisfactorily
as long as we carefully adjust those factors such as the etching time and the
thickness of the evaporated layers. The error in the junction number is within
. By additional ion etching if necessary, we can controllably decrease
the junction number to a rather small value, and even a single intrinsic
Josephson junction can be produced.Comment: to bu published in Jpn. J. Appl. Phys., 43(7A) 200
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