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 $\eta_C/2$ and $\eta_C/(2-\eta_C)$, $\eta_C /2$ and $\eta_C$, 0 and $\eta_C/(2-\eta_C)$, 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