Search results for "Activity"
showing 10 items of 7178 documents
Coronal properties of active G-type stars in different evolutionary phases
2005
We report on the analysis of XMM-Newton observations of three G-type stars in very different evolutionary phases: the "weak-line" T Tauri star HD 283572, the Zero Age Main Sequence star EK Dra and the Hertzsprung-gap giant star 31 Corn. The X-ray luminosities of the three stars are all in the range 10(30) - 10(31) erg/s. We compare the Emission Measure Distributions of these bright sources, derived from high-resolution X-ray spectra, as well as the pattern of elemental abundances vs. First Ionization Potential (FIP). The results of our analysis suggest that the coronae of these stars are very similar in terms of dominant coronal magnetic structures, in spite of differences in their evolutio…
High Energy Emission and its Variability in Young Stellar Objects
2019
Young stars show a variety of highly energetic phenomena, from accretion and outflow processes to hot coronal plasmas confined in their outer atmosphere, all regulated by the intense stellar magnetic fields. Many aspects on each of these phenomena are debated, but, most notably, their complex mutual interaction remains obscure. In this work I report how these phenomena are simultaneously responsible for the high-energy emission from young stars, with a special focus on the expected and observed variability in the X-ray band. Investigating variations in the X-ray emission from young stars allows us to pose constraints on flare and coronal plasma properties, coronal heating, accretion stream …
Activity-rotation relation in the young cluster h Per
2015
The activity-rotation relation in PMS stars is still an open issue. To bridge the gap between the well constrained case of MS stars and the puzzling case of very young PMS stars, we studied the activity-rotation relation in the young cluster h Persei. Because of its age (˜13 Myr) h Per contains both fast and slow rotators, allowing us therefore to test the different regimes of stellar dynamo. We analyzed a deep Chandra/ACIS-I observation to constrain the activity level of h Per members. Rotational periods were derived by tet{MorauxArtemenko2013}. From the comparison of the 1002 detected X-ray sources, and the 586 h Per members with measured rotational period, we obtained a final catalog of …
Simbol-X capability of detecting the non-thermal emission of stellar flares.
2008
We investigate the capability of detecting, with Simbol-X, non-thermal emission during stellar flares, and distinguishing it from hot thermal emission. We find that flare non-thermal emission is detectable when at least ~20 cts are detected with the CZT detector in the 20-80 keV band. Therefore Simbol-X will detect the non-thermal emission from some of the X-ray brightest nearby stars, whether the thermal vs. non-thermal relation, derived for solar flares, holds.
CSI 2264: Simultaneous optical and X-ray variability in the pre-main sequence stars of NGC 2264
2019
Context. Pre-main sequence stars are variable sources. In diskless stars this variability is mainly due to the rotational modulation of dark photospheric spots and active regions, as in main sequence stars even if associated with a stronger magnetic activity.Aims. We aim at analyzing the simultaneous optical and X-ray variability in these stars to unveil how the activity in the photosphere is connected with that in the corona, to identify the dominant surface magnetic activity, and to correlate our results with stellar properties, such as rotation and mass.Methods. We analyzed the simultaneous optical and X-ray variability in stars without inner disks (e.g., class III objects and stars with…
Inconsistencies in the pozzolanic strength activity index (SAI) for silica fume according to EN and ASTM
2014
Published version of an article in the journal: Materials and Structures. Also available from the publisher at: http://dx.doi.org/10.1617/s11527-014-0457-6 Open Access New supplementary cementitious materials claimed to possess pozzolan properties emerge frequently. This development is driven both by economic and environmental pressures. Properties of new materials are compared with those of materials already well known, such as silica fume. Several test methods are standardized for making such comparisons, regulated by both European (EN) and American (ASTM) standards. Standardization indicates that procedures are secured to make comparisons valid and informative. In this article the sensit…
Stress and physical activity during a 1-year counseling intervention
2013
TIIVISTELMÄ Schildt, Kasimir Ario Vilhelm 2013. Stressi ja fyysinen aktiivisuus vuoden mittaisen neuvonta intervention aikana. Liikuntafysiologian Pro gradu -tutkielma. Liikuntabiologian laitos. Jyväskylän yliopisto. 83 sivua. Liikkumattomuus on luokiteltu maailman neljänneksi suurimmaksi kuolinsyyksi ja arviolta 3,2 miljoonaa ihmista kuolee vuosittain liikkumattomuudesta seuraaviin sairauksiin. Samaan aikaan ihmisten kokema stressi on lisääntynyt. Monissa aiemmissa tutkimuksissa fyysisen aktiivisuuden lisääminen on helpottanut stressiä. Tämän tutkimuksen tarkoitus oli selvittää, ovatko fyysinen aktiivisuus ja inaktiivisuus yhteydessä koettuun ja sykevälivaihtelun avulla mitattuun stressiin…
Design, synthesis and structure-activity relationship of 2-(3',4',5'-trimethoxybenzoyl)-benzo[b]furan derivatives as a novel class of inhibitors of t…
2009
The biological importance of microtubules in mitosis and cell division makes them an interesting target for the development of anticancer agents. Small molecules such as benzo[b]furans are attractive as inhibitors of tubulin polymerization. Thus, a new class of inhibitors of tubulin polymerization based on the 2-(3′,4′,5′-trimethoxybenzoyl)-benzo[b]furan molecular skeleton, with electron-donating (Me, OMe or OH) or electron-withdrawing (F, Cl and Br) substituents on the benzene ring, was synthesized and evaluated for antiproliferative activity, inhibition of tubulin polymerization and cell cycle effects. Adding a methyl group at the C-3 position resulted in increased activity. The most prom…
Autorreflexión pedagógica
2019
The autobiographical reflection on school learning makes it possible to explain how personal life guidelines are loading teaching activity with experiences. Educational time does not consist only of a linear narration, but works as the evocation of temporal and spatial memories of an explanation of the present. Personal life is intertwined with school reflection to give meaning to what we decide from teaching
Uz stāstiem balstīti uzdevumi angļu valodas teksta izpratnes pilnveidei vidusskolā
2015
Diplomdarba nosaukums ir „Uz stāstiem balstīti uzdevumi angļu valodas teksta izpratnes pilnveidei vidusskolā”. Izvirzītais darba mērķis ir noskaidrot, kā uz stāstiem balstīti uzdevumi var palīdzēt pilnveidot vidusskolēnu teksta izpratni angļu valodas stundās. Atsevišķa gadījuma pētījums ir izvēlēts kā pētījuma metode, kas tika realizēts Siguldas Valsts ģimnāzijas 10. klases angļu valodas stundās. Tās dalībnieki bija 13 skolēni. Pētījuma laikā skolēni tika anketēti, analizēta skolēnu attieksme pret viņu obligātajiem mācību grāmatas tekstiem un viņu lasīšanas izpratne, aprakstīta skolēnu darbošanās angļu valodas stundās, kurās bija iekļauti uz stāstiem balstīti uzdevumi, un analizēta skolēnu …