Coronal Loops with Different Metallicities and Generalized RTV Scaling Laws

Stellar metallicity is a critical factor to characterize the stellar coronae because it directly affects the radiative energy loss from the atmosphere. By extending theoretical relations for solar coronal loops introduced by \cite{Rosner1978}, we analytically derive scaling relations for stellar coronal loops with various metallicities. In order to validate the derived relations, we also perform magnetohydrodyamic simulations for the heating of coronal loops with different metallicities by changing radiative loss functions according to the adopted elemental abundances. The simulation results nicely explain the generalized analytical scaling relations and show a strong dependence of the thermodynamical and radiative properties of the loops on metallicity. Higher density and temperature are obtained in lower-metallicity coronae because of the inefficient radiative cooling, provided that the surface condition is unchanged. Thus, it is estimated that the X-ray radiation from metal-poor coronae is higher because of their denser coronal gas. The generalized scaling laws can also be used as a tool to study the condition of high-energy radiation around magnetically active stars and their impact on planetary environments.Comment: 14 pages, 12 figures, accepted to Ap

Physical gelation by amides derived from trans-1, 2-diaminocyclohexane and their tetrasiloxane-based gelators

Four compounds were prepared from trans-1,2-diaminocyclohexane and were subsequently studied as gelators. These two compounds were chiral trans-(1R,2R)-1-(2-heptylundecanoylamino)-2-(10-undecenoylamino) cyclohexane and the corresponding racemate. The other two compounds were 1,1,3,3,5,5,7,7-octamethyltetrasiloxane-containing chiral and racemic compounds prepared by a hydrosilylation reaction. Their gelation abilities were evaluated on the basis of the minimum gel concentration, using seven solvents. The thermal stability and transparency of the gels were investigated by UV-vis spectroscopy using three-component mixed solvents of hexadecyl 2-ethylhexanoate, liquid paraffin, and decamethylcyclopentasiloxane (66 combinations). The gel-to-sol phase-transition temperatures were also studied. The viscoelastic behavior of the gels was studied by rheology measurements in the strain sweep mode. Aggregates consisting of three-dimensional networks were studied by transmission electron microscopy. Circular dichroism spectroscopy was performed to verify the existence of helical aggregates in the gel.ArticlePOLYMER JOURNAL.49(5):439-447(2017)journal articl

Shortest Reconfiguration of Colorings Under Kempe Changes

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