18,044 research outputs found
Constraints on the Heating of High Temperature Active Region Loops: Observations from Hinode and SDO
We present observations of high temperature emission in the core of a solar
active region using instruments on Hinode and SDO. These multi-instrument
observations allow us to determine the distribution of plasma temperatures and
follow the evolution of emission at different temperatures. We find that at the
apex of the high temperature loops the emission measure distribution is
strongly peaked near 4 MK and falls off sharply at both higher and lower
temperatures. Perhaps most significantly, the emission measure at 0.5 MK is
reduced by more than two orders of magnitude from the peak at 4 MK. We also
find that the temporal evolution in broad-band soft X-ray images is relatively
constant over about 6 hours of observing. Observations in the cooler SDO/AIA
bandpasses generally do not show cooling loops in the core of the active
region, consistent with the steady emission observed at high temperatures.
These observations suggest that the high temperature loops observed in the core
of an active region are close to equilibrium. We find that it is possible to
reproduce the relative intensities of high temperature emission lines with a
simple, high-frequency heating scenario where heating events occur on time
scales much less than a cooling time. In contrast, low-frequency heating
scenarios, which are commonly invoked to describe nanoflare models of coronal
heating, do not reproduce the relative intensities of high temperature emission
lines and predict low-temperature emission that is approximately an order of
magnitude too large. We also present an initial look at images from the SDO/AIA
94 A channel, which is sensitive to Fe XVIII.Comment: Movies are available at
http://tcrb.nrl.navy.mil/~hwarren/temp/papers/active_region_core/ Paper has
been refereed and revise
Observation and Modeling of Coronal "Moss" With the EUV Imaging Spectrometer on Hinode
Observations of transition region emission in solar active regions represent
a powerful tool for determining the properties of hot coronal loops. In this
Letter we present the analysis of new observations of active region moss taken
with the Extreme Ultraviolet Imaging Spectrometer (EIS) on the \textit{Hinode}
mission. We find that the intensities predicted by steady, uniformly heated
loop models are too intense relative to the observations, consistent with
previous work. To bring the model into agreement with the observations a
filling factor of about 16% is required. Furthermore, our analysis indicates
that the filling factor in the moss is nonuniform and varies inversely with the
loop pressure
Targeted Assembly of Short Sequence Reads
As next-generation sequence (NGS) production continues to increase, analysis is becoming a significant bottleneck. However, in situations where information is required only for specific sequence variants, it is not necessary to assemble or align whole genome data sets in their entirety. Rather, NGS data sets can be mined for the presence of sequence variants of interest by localized assembly, which is a faster, easier, and more accurate approach. We present TASR, a streamlined assembler that interrogates very large NGS data sets for the presence of specific variants, by only considering reads within the sequence space of input target sequences provided by the user. The NGS data set is searched for reads with an exact match to all possible short words within the target sequence, and these reads are then assembled strin-gently to generate a consensus of the target and flanking sequence. Typically, variants of a particular locus are provided as different target sequences, and the presence of the variant in the data set being interrogated is revealed by a successful assembly outcome. However, TASR can also be used to find unknown sequences that flank a given target. We demonstrate that TASR has utility in finding or confirming ge-nomic mutations, polymorphism, fusion and integration events. Targeted assembly is a powerful method for interrogating large data sets for the presence of sequence variants of interest. TASR is a fast, flexible and easy to use tool for targeted assembly
Large Area Crop Inventory Experiment (LACIE). User requirements
There are no author-identified significant results in this report
Constructing Gravity Amplitudes from Real Soft and Collinear Factorisation
Soft and collinear factorisations can be used to construct expressions for
amplitudes in theories of gravity. We generalise the "half-soft" functions used
previously to "soft-lifting" functions and use these to generate tree and
one-loop amplitudes. In particular we construct expressions for MHV tree
amplitudes and the rational terms in one-loop amplitudes in the specific
context of N=4 supergravity. To completely determine the rational terms
collinear factorisation must also be used. The rational terms for N=4 have a
remarkable diagrammatic interpretation as arising from algebraic link diagrams.Comment: 18 pages, axodraw, Proof of eq. 4.3 adde
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