252,949 research outputs found
On Flux Rope Stability and Atmospheric Stratification in Models of Coronal Mass Ejections Triggered by Flux Emergence
Flux emergence is widely recognized to play an important role in the
initiation of coronal mass ejections. The Chen-Shibata (2000) model, which
addresses the connection between emerging flux and flux rope eruptions, can be
implemented numerically to study how emerging flux through the photosphere can
impact the eruption of a pre-existing coronal flux rope. The model's
sensitivity to the initial conditions and reconnection micro-physics is
investigated with a parameter study. In particular, we aim to understand the
stability of the coronal flux rope in the context of X-point collapse and the
effects of boundary driving in both unstratified and stratified atmospheres. In
the absence of driving, we assess the behavior of waves in the vicinity of the
X-point. With boundary driving applied, we study the effects of reconnection
micro-physics and atmospheric stratification on the eruption. We find that the
Chen-Shibata equilibrium can be unstable to an X-point collapse even in the
absence of driving due to wave accumulation at the X-point. However, the
equilibrium can be stabilized by reducing the compressibility of the plasma,
which allows small-amplitude waves to pass through the X-point without
accumulation. Simulations with the photospheric boundary driving evaluate the
impact of reconnection micro-physics and atmospheric stratification on the
resulting dynamics: we show the evolution of the system to be determined
primarily by the structure of the global magnetic fields with little
sensitivity to the micro-physics of magnetic reconnection; and in a stratified
atmosphere, we identify a novel mechanism for producing quasi-periodic behavior
at the reconnection site behind a rising flux rope as a possible explanation of
similar phenomena observed in solar and stellar flares.Comment: Submitted Feb 28, 2014 to, accepted Aug 14, 2014 by Astronomy &
Astrophysics. 13 pages, 10 figures, 2 table
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Getting creative in everyday life: Investigating arts and crafts hobbyists' information behavior
While there has been increasing interest in how creative professionals find information to drive creative outputs, previous information behavior research has largely ignored how arts and crafts hobbyists look for information sources in their everyday lives. To fill this literature gap, we conducted interviews and observations with arts and crafts hobbyists to find out how they conceive potential DIY projects. The findings highlight three themes: the dearth of human sources, the prevalence of domain-specific information, and the use of self-curated information. In addition to empirical results, this work also broadens the understanding of information behavior in an arts and crafts context by studying populations beyond professional artists
Clearigate ® Treatments for Control of Giant Salvinia
Results of recent field trials using the chelated copper formulation
Clearigate®
4
showed that applying a 20% solution
by volume was effective for controlling populations of giant
salvinia in irrigation canals.
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Lower rates may be efficacious,
thereby reducing chemical use and cost; however, little is
known about the dose-response effects of Clearigate®
against giant salvinia. The objective of this study was to determine
the effective rate range of chelated copper applied as
Clearigate® for control of giant salvinia
Poisson Brackets of Normal-Ordered Wilson Loops
We formulate Yang-Mills theory in terms of the large-N limit, viewed as a
classical limit, of gauge-invariant dynamical variables, which are closely
related to Wilson loops, via deformation quantization. We obtain a Poisson
algebra of these dynamical variables corresponding to normal-ordered quantum
(at a finite value of ) operators. Comparing with a Poisson algebra one
of us introduced in the past for Weyl-ordered quantum operators, we find, using
ideas closly related to topological graph theory, that these two Poisson
algebras are, roughly speaking, the same. More precisely speaking, there exists
an invertible Poisson morphism between them.Comment: 34 pages, 4 eps figures, LaTeX2.09; citations adde
Critical behavior in ultra-strong-coupled oscillators
We investigate the strong coupling regime of a linear - coupled
harmonic oscillator system, by performing a direct diagonalization of the
hamiltonian. It is shown that the - coupled hamiltonian can be
equivalently described by a Mach-Zehnder-type interferometer with a quadratic
unitary operation in each of its arms. We show a sharp transition of the
unitary operation from an elliptical phase rotator to an elliptical squeezer as
the coupling gets stronger, which leads to the continuous generation of
entanglement, even for a significantly thermal state, in the ultra-strong
coupled regime. It is also shown that this critical regime cannot be achieved
by a classical Hookian coupling. Finally, the effect of a finite-temperature
environment is analyzed, showing that entanglement can still be generated from
a thermal state in the ultra-strong coupled regime, but is destroyed rapidly
Safely dissolvable and healable active packaging films based on alginate and pectin
Extensive usage of long-lasting petroleum based plastics for short-lived application such as packaging has raised concerns regarding their role in environmental pollution. In this research, we have developed active, healable, and safely dissolvable alginate-pectin based biocomposites that have potential applications in food packaging. The morphological study revealed the rough surface of these biocomposite films. Tensile properties indicated that the fabricated samples have mechanical properties in the range of commercially available packaging films while possessing excellent healing effciency. Biocomposite films exhibited higher hydrophobicity properties compared to neat alginate films. Thermal analysis indicated that crosslinked biocomposite samples possess higher thermal stability in temperatures below 120 °C, while antibacterial analysis against E. coli and S. aureus revealed the antibacterial properties of the prepared samples against different bacteria. The fabricated biodegradable multi-functional biocomposite films possess various imperative properties, making them ideal for utilization as packaging material
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