18,966 research outputs found
Radiance and Doppler shift distributions across the network of the quiet Sun
The radiance and Doppler-shift distributions across the solar network provide
observational constraints of two-dimensional modeling of transition-region
emission and flows in coronal funnels. Two different methods, dispersion plots
and average-profile studies, were applied to investigate these distributions.
In the dispersion plots, we divided the entire scanned region into a bright and
a dark part according to an image of Fe xii; we plotted intensities and Doppler
shifts in each bin as determined according to a filtered intensity of Si ii. We
also studied the difference in height variations of the magnetic field as
extrapolated from the MDI magnetogram, in and outside network. For the
average-profile study, we selected 74 individual cases and derived the average
profiles of intensities and Doppler shifts across the network. The dispersion
plots reveal that the intensities of Si ii and C iv increase from network
boundary to network center in both parts. However, the intensity of Ne viii
shows different trends, namely increasing in the bright part and decreasing in
the dark part. In both parts, the Doppler shift of C iv increases steadily from
internetwork to network center. The average-profile study reveals that the
intensities of the three lines all decline from the network center to
internetwork region. The binned intensities of Si ii and Ne viii have a good
correlation. We also find that the large blue shift of Ne viii does not
coincide with large red shift of C iv. Our results suggest that the network
structure is still prominent at the layer where Ne viii is formed in the quiet
Sun, and that the magnetic structures expand more strongly in the dark part
than in the bright part of this quiet Sun region.Comment: 10 pages,9 figure
Phonon anomaly in BaFe2As2
The detailed optical properties of BaFe2As2 have been determined over a wide
frequency range above and below the structural and magnetic transition at T_N =
138 K. A prominent in-plane infrared-active mode is observed at 253 cm^{-1}
(31.4 meV) at 295 K. The frequency of this vibration shifts discontinuously at
T_N; for T < T_N the frequency of this mode displays almost no temperature
dependence, yet it nearly doubles in intensity. This anomalous behavior appears
to be a consequence of orbital ordering in the Fe-As layers.Comment: 4 pages, 3 figures and one table (minor revisions
Upflows in the upper transition region of the quiet Sun
We investigate the physical meaning of the prominent blue shifts of Ne VIII,
which is observed to be associated with quiet-Sun network junctions (boundary
intersections), through data analyses combining force-free-field extrapolations
with EUV spectroscopic observations. For a middle-latitude region, we
reconstruct the magnetic funnel structure in a sub-region showing faint
emission in EIT-Fe 195. This funnel appears to consist of several smaller
funnels that originate from network lanes, expand with height and finally merge
into a single wide open-field region. However, the large blue shifts of Ne VIII
are generally not associated with open fields, but seem to be associated with
the legs of closed magnetic loops. Moreover, in most cases significant upflows
are found in both of the funnel-shaped loop legs. These quasi-steady upflows
are regarded as signatures of mass supply to the coronal loops rather than the
solar wind. Our observational result also reveals that in many cases the
upflows in the upper transition region (TR) and the downflows in the middle TR
are not fully cospatial. Based on these new observational results, we suggest
different TR structures in coronal holes and in the quiet Sun.Comment: 4 pages, 4 figures, will appear in the Proceedings of the Solar wind
12 conferenc
Bounds of Efficiency at Maximum Power for Normal-, Sub- and Super-Dissipative Carnot-Like Heat Engines
The Carnot-like heat engines are classified into three types (normal-, sub-
and super-dissipative) according to relations between the minimum irreversible
entropy production in the "isothermal" processes and the time for completing
those processes. The efficiencies at maximum power of normal-, sub- and
super-dissipative Carnot-like heat engines are proved to be bounded between
and , and , 0 and
, respectively. These bounds are also shared by linear, sub-
and super-linear irreversible Carnot-like engines [Tu and Wang, Europhys. Lett.
98, 40001 (2012)] although the dissipative engines and the irreversible ones
are inequivalent to each other.Comment: 1 figur
Connexin-hemichannels are Involved in Acidosis-induced ATP Release from Skeletal Myocytes
Oral PresentationATP is an important extracellular signalling molecule which contributes to
exercise vasodilation. We have previously shown that the cystic fibrosis
transmembrane conductance regulator (CFTR) is involved in acidosis-induced
ATP release from skeletal muscle. However, it is still unknown whether ATP
is released through CFTR itself or whether CFTR regulates a separate ATPrelease
channel. So we investigated: (1) the pathway responsible for CFTR
activation in myocytes at low pH; (2) whether connexin (Cx) hemichannels
were involved in the acidosis-induced ATP release from skeletal muscle.
Lactic acid (10 mM) increased the intracellular cAMP and the extracellular
ATP in L6 skeletal myocytes. Similarly, the cAMP-elevating agent, forskolin,
increased extracellular ATP. The phosphodiesterase inhibitor, IBMX,
increased extracellular ATP in the absence or presence of lactic acid. CFTR
phosphorylation was increased by the addition of forskolin alone, and further
increased by forskolin plus dibutyryl-cAMP and IBMX, but the forskolininduced
increase in CFTR phosphorylation was inhibited by the PKA inhibitor,
KT5720. Whereas KT5720 inhibited acidosis-induced ATP release from
myocytes. These data suggest that skeletal muscle CFTR is activated through
the cAMP/PKA pathway at low pH. RT-PCR indicated that cultured rat L6
skeletal myocytes expressed mRNA for both Cx40 and Cx43, but Cx40 was
expressed only weakly in western blot, whereas Cx43 was strongly expressed.
Co-immunoprecipitation results showed that CFTR and Cx43 were associated
with each other in the cell membrane. A Cx43 over-expression model was created by transfecting myocytes with a Cx43 plasmid: Cx43 over-expression
was confirmed using western blot. Cx43 over-expressing myocytes released
significantly more ATP than control myocytes at pH 6.8, suggesting that
Cx43 may be involved in acidosis-induced ATP release, whereas silencing
Cx43 expression using siRNA inhibited the acidosis-induced ATP release.
Over-expression of CFTR alone did not alter ATP release from myocytes,
whereas co-over-expression of CFTR with Cx43 increased ATP release
significantly more than over-expression of Cx43 alone. These data suggest
that Cx43 co-localises with CFTR in the myocyte membrane, and that it
may be involved in ATP release during acidosis; further investigation is
required to determine whether and how CFTR interacts with Cx43 to induce
ATP release.published_or_final_versio
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