350 research outputs found
The influence of oscillations on energy estimates for damped wave models with time-dependent propagation speed and dissipation
The aim of this paper is to derive higher order energy estimates for
solutions to the Cauchy problem for damped wave models with time-dependent
propagation speed and dissipation. The model of interest is \begin{equation*}
u_{tt}-\lambda^2(t)\omega^2(t)\Delta u +\rho(t)\omega(t)u_t=0, \quad
u(0,x)=u_0(x), \,\, u_t(0,x)=u_1(x). \end{equation*} The coefficients
and are shape functions and
is an oscillating function. If and
is an "effective" dissipation term, then energy
estimates are proved in [2]. In contrast, the main goal of the present paper is
to generalize the previous results to coefficients including an oscillating
function in the time-dependent coefficients. We will explain how the interplay
between the shape functions and oscillating behavior of the coefficient will
influence energy estimates.Comment: 37 pages, 2 figure
Magnetic domain observation of hydrogenation disproportionation desorption recombination processed Ndļ¼Feļ¼B powder with a high-resolution Kerr microscope using ultraviolet light
A Kerr microscope that uses ultraviolet (UV) light for high-resolution domain observation was built, and the domain structure and magnetization process of hydrogenation disproportionation desorption recombination (HDDR) powder were examined. The UV Kerr microscope could observe nanometer-sized domain patterns. Applying a dc field of 1.0 kOe to HDDR powder at a desorption recombination (DR) time of 12 min produced abrupt wall motion. The pinning force exerted by the grain boundaries is inadequate for producing high coercivity because the Nd-rich phase layers along these boundaries are absent at a DR time of 12 min. For HDDR powder at a DR time greater than 14 min, changing the magnetic field by up to 1.0 kOe produced no observable wall motion. It follows that the high coercivity of HDDR powder is due to domain wall pinning at the grain boundaries
Cholesterol- and actin-centered view of the plasma membrane: updating the SingerāNicolson fluid mosaic model to commemorate its 50th anniversary
Two very polarized views exist for understanding the cellular plasma membrane (PM). For some, it is the simple fluid described by the original SingerāNicolson fluid mosaic model. For others, due to the presence of thousands of molecular species that extensively interact with each other, the PM forms various clusters and domains that are constantly changing and therefore, no simple rules exist that can explain the structure and molecular dynamics of the PM. In this article, we propose that viewing the PM from its two predominant components, cholesterol and actin filaments, provides an excellent and transparent perspective of PM organization, dynamics, and mechanisms for its functions. We focus on the actin-induced membrane compartmentalization and lipid raft domains coexisting in the PM and how they interact with each other to perform PM functions. This view provides an important update of the fluid mosaic model
Global well-posedness of the Kirchhoff equation and Kirchhoff systems
This article is devoted to review the known results on global well-posedness
for the Cauchy problem to the Kirchhoff equation and Kirchhoff systems with
small data. Similar results will be obtained for the initial-boundary value
problems in exterior domains with compact boundary. Also, the known results on
large data problems will be reviewed together with open problems.Comment: arXiv admin note: text overlap with arXiv:1211.300
Near-Infrared H and K band studies of the 2006 outburst of the recurrent nova RS Ophiuchi
We present near-IR photo-spectroscopy in the H and K bands of the 2006
outburst of the recurrent nova RS Ophiuchi (RS Oph). The observations cover the
period between 1 to 94 days after the eruption. The near IR light curve and an
extensive set of spectra are presented, lines identified and the general
characteristics of the spectra discussed. Analysis of the HI line profiles show
the presence of broad wings on both flanks of a strong central component
indicating the presence of a bipolar velocity flow in the ejecta. Such a flow
is kinematically consistent with the bipolar structure that the object displays
in high-resolution spatial images. We discuss the behaviour and origin of the
Fe II lines at 1.6872 and 1.7414 micron and show that Lyman alpha and Lyman
continuum fluorescence are viable mechanisms to excite these lines. We draw
upon the result, that collisional excitation can also contribute in exciting
and significantly enhancing the strength of these Fe II lines, to propose that
these lines originate from a site of high particle density. Such a likely site
could be the high-density, low temperature contact surface that should exist in
the shockfront in between the shocked ejecta and red giant wind. Recombination
analysis of the HI lines indicate deviations from Case B conditions during most
of the span of our observations indicating optical depth effects. It appears
likely that the breakout of the shockfront had not yet occured till the end of
our observations. An analysis is made of the temporal evolution of the [Si VI]
1.9641 micron coronal line and another coronal line at 2.0894 micron which is
attributed to [Mn XIV]. Assuming collisional effects to dominate in the hot
coronal gas, estimates are made of the ion temperature in the gas.Comment: Accepted in MNRAS. Accepted version with inclusion of additional
analysi
- ā¦