4,289 research outputs found
The Relation between Solar Eruption Topologies and Observed Flare Features I: Flare Ribbons
In this paper we present a topological magnetic field investigation of seven
two-ribbon flares in sigmoidal active regions observed with Hinode, STEREO, and
SDO. We first derive the 3D coronal magnetic field structure of all regions
using marginally unstable 3D coronal magnetic field models created with the
flux rope insertion method. The unstable models have been shown to be a good
model of the flaring magnetic field configurations. Regions are selected based
on their pre-flare configurations along with the appearance and observational
coverage of flare ribbons, and the model is constrained using pre-flare
features observed in extreme ultraviolet and X-ray passbands. We perform a
topology analysis of the models by computing the squashing factor, Q, in order
to determine the locations of prominent quasi-separatrix layers (QSLs). QSLs
from these maps are compared to flare ribbons at their full extents. We show
that in all cases the straight segments of the two J-shaped ribbons are matched
very well by the flux-rope-related QSLs, and the matches to the hooked segments
are less consistent but still good for most cases. In addition, we show that
these QSLs overlay ridges in the electric current density maps. This study is
the largest sample of regions with QSLs derived from 3D coronal magnetic field
models, and it shows that the magnetofrictional modeling technique that we
employ gives a very good representation of flaring regions, with the power to
predict flare ribbon locations in the event of a flare following the time of
the model
A synthesis of sand seas throughout the world
There are no author-identified significant results in this report
Testing statistical learning implicitly: A novel chunk-based measure of statistical learning
Attempts to connect individual differences in statistical learning with broader aspects of cognition have received considerable attention, but have yielded mixed results. A possible explanation is that statistical learning is typically tested using the two-alternative forced choice (2AFC) task. As a meta-cognitive task relying on explicit familiarity judgments, 2AFC may not accurately capture implicitly formed statistical computations. In this paper, we adapt the classic serial-recall memory paradigm to implicitly test statistical learning in a statistically-induced chunking recall (SICR) task. We hypothesized that artificial language exposure would lead subjects to chunk recurring statistical patterns, facilitating recall of words from the input. Experiment 1 demonstrates that SICR offers more fine-grained insights into individual differences in statistical learning than 2AFC. Experiment 2 shows that SICR has higher test-retest reliability than that reported for 2AFC. Thus, SICR offers a more sensitive measure of individual differences, suggesting that basic chunking abilities may explain statistical learning
Modeling near-field radiative heat transfer from sharp objects using a general 3d numerical scattering technique
We examine the non-equilibrium radiative heat transfer between a plate and
finite cylinders and cones, making the first accurate theoretical predictions
for the total heat transfer and the spatial heat flux profile for
three-dimensional compact objects including corners or tips. We find
qualitatively different scaling laws for conical shapes at small separations,
and in contrast to a flat/slightly-curved object, a sharp cone exhibits a local
\emph{minimum} in the spatially resolved heat flux directly below the tip. The
method we develop, in which a scattering-theory formulation of thermal transfer
is combined with a boundary-element method for computing scattering matrices,
can be applied to three-dimensional objects of arbitrary shape.Comment: 5 pages, 4 figures. Corrected background information in the
introduction, results and discussion unchange
Variability in H9N2 haemagglutinin receptor-binding preference and the pH of fusion
H9N2 avian influenza viruses are primarily a disease of poultry; however, they occasionally infect humans and are considered a potential pandemic threat. Little work has been performed to assess the intrinsic biochemical properties related to zoonotic potential of H9N2 viruses. The objective of this study, therefore, was to investigate H9N2 haemagglutinins (HAs) using two well-known correlates for human adaption: receptor-binding avidity and pH of fusion. Receptor binding was characterized using bio-layer interferometry to measure virus binding to human and avian-like receptor analogues and the pH of fusion was assayed by syncytium formation in virus-infected cells at different pHs. We characterized contemporary H9N2 viruses of the zoonotic G1 lineage, as well as representative viruses of the zoonotic BJ94 lineage. We found that most contemporary H9N2 viruses show a preference for sulphated avian-like receptor analogues. However, the ‘Eastern’ G1 H9N2 viruses displayed a consistent preference in binding to a human-like receptor analogue. We demonstrate that the presence of leucine at position 226 of the HA receptor-binding site correlated poorly with the ability to bind a human-like sialic acid receptor. H9N2 HAs also display variability in their pH of fusion, ranging between pH 5.4 and 5.85 which is similar to that of the first wave of human H1N1pdm09 viruses but lower than the pH of fusion seen in zoonotic H5N1 and H7N9 viruses. Our results suggest possible molecular mechanisms that may underlie the relatively high prevalence of human zoonotic infection by particular H9N2 virus lineages
Light quality regulates expression of chloroplast genes and assembly of photosynthetic membrane complexes
Dispersal, niche breadth and population extinction: colonization ratios predict range size in N orth A merican dragonflies
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/107541/1/jane12181.pd
Kansas environmental and resource study: A Great Plains model, tasks 1-6
There are no author identified significant results in this report. Environmental and resources investigations in Kansas utilizing ERTS-1 imagery are summarized for the following areas: (1) use of feature extraction techniqued for texture context information in ERTS imagery; (2) interpretation and automatic image enhancement; (3) water use, production, and disease detection and predictions for wheat; (4) ERTS-1 agricultural statistics; (5) monitoring fresh water resources; and (6) ground pattern analysis in the Great Plains
Microstructure Effects for Casimir Forces in Chiral Metamaterials
We examine a recent prediction for the chirality-dependence of the Casimir
force in chiral metamaterials by numerical computation of the forces between
the exact microstructures, rather than homogeneous approximations. We compute
the exact force for a chiral bent-cross pattern, as well as forces for an
idealized "omega"-particle medium in the dilute approximation and identify the
effects of structural inhomogeneity (i.e. proximity forces and anisotropy). We
find that these microstructure effects dominate the force for separations where
chirality was predicted to have a strong influence. To get observations of
chirality free from microstructure effects, one must go to large separations
where the effect of chirality is at most of the total force.Comment: 5 pages, 4 figure
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