698 research outputs found
The different origins of magnetic fields and activity in the Hertzsprung gap stars, OU Andromedae and 31 Comae
Context: When crossing the Hertzsprung gap, intermediate-mass stars develop a
convective envelope. Fast rotators on the main sequence, or Ap star
descendants, are expected to become magnetic active subgiants during this
evolutionary phase. Aims: We compare the surface magnetic fields and activity
indicators of two active, fast rotating red giants with similar masses and
spectral class but diferent rotation rates - OU And (Prot=24.2 d) and 31 Com
(Prot=6.8 d) - to address the question of the origin of their magnetism and
high activity.
Methods: Observations were carried out with the Narval spectropolarimeter in
2008 and 2013.We used the least squares deconvolution technique to extract
Stokes V and I profiles to detect Zeeman signatures of the magnetic field of
the stars. We provide Zeeman-Doppler imaging, activity indicator monitoring,
and a precise estimation of stellar parameters. We use stellar evolutionary
models to infer the evolutionary status and the initial rotation velocity on
the main sequence.
Results: The detected magnetic field of OU And is a strong one. Its
longitudinal component Bl reaches 40 G and presents an about sinusoidal
variation with reversal of the polarity. The magnetic topology of OU And is
dominated by large scale elements and is mainly poloidal with an important
dipole component, and a significant toroidal component. The detected magnetic
field of 31 Com is weaker, with a magnetic map showing a more complex field
geometry, and poloidal and toroidal components of equal contributions. The
evolutionary models show that the progenitors of OU And and 31 Com must have
been rotat
Conclusions: OU And appears to be the probable descendant of a magnetic Ap
star, and 31 Com the descendant of a relatively fast rotator on the main
sequence.Comment: 16 pages, 12 figure
Effect of nitrogenous bases on the thermal stability of jet fuels
Fuels from naphthenic petroleums were evaluated, and it was found that they had more N bases than those paraffinic ones (0.00024 and 0.000009% N, respectively). The removal of the N bases improved significantly the thermal stability and reduced the residue formation during oxidation of the fuel. The improvement depended on both content and composition of the bases. Thus, fuels with similar content of N bases (0.00058% N) and thermal stability had oxidation residues of 17.5 and 5.6 and sol. gum of 13 and 1.5 mg/100 ml, before and after removing the N bases, respectively
Influence of Fruit Juice From Aronia Melanocarpa on the Process of Lipid Peroxidation in a Model of Carbon Tetrachloride-Induced Hepatotoxicity in Rats
The fruit juice from Aronia melanocarpa (FJAM) is rich in anthocyanins. We studied the effect of FJAM on the process of lipid peroxidation in a model of carbon tetrachloride (CCI4)-induced hepatotoxicity in rats. Malondialdehyde (MDA) levels were measured in plasma and liver homogenate. CCU induced a significant elevation of MDA levels in the plasma (p<0,05) and in the homogenate (p<0,01) in comparison with distilled water-treated controls. FJAM applied alone did not significantly influence on the MDA levels. The pretreatment of the rats with FJAM before their treatment with CCI4 lead dose-dependently to MDA levels in the plasma and homogenate which did not differ in most animal groups from the controls and were significantly lower from those of the CCI4-treated rats
Antiproliferative activity of a new derivative from the class of N-glycoside of indolo [2,3-a] pyrrolo [3,4-c] carbazoles
The aim of the study was to evaluate an antiproliferative activity of a new, Russian derivative of N-glycoside substituted indolocarbazole 6-amino-12-(α-L-arabinopyranosyl)indolo [2,3-a] pyrrolo [3,4-c] carbazole-5,7-dione (LCS-1208) on models of transplantable tumors of mice and on human tumors in Balb/c nude mic
Methodical recommendation to "Basics of software engineering. Laboratory practice". Part 1
Software engineering is an engineering discipline that is concerned with all aspects of software production. Software engineering can be divided into sub-disciplines. Some of them are: - Software engineering management: The application of management activities – planning, coordinating, measuring, monitoring, controlling, and reporting – to ensure that the development and maintenance of software is systematic, disciplined, and quantified. Requirements engineering: The elicitation, analysis, specification, and validation of requirements for software
Methodical recommendation to "Basics of software engineering. Laboratory practice". Part 1
Software engineering is an engineering discipline that is concerned with all aspects of software production. Software engineering can be divided into sub-disciplines. Some of them are: - Software engineering management: The application of management activities – planning, coordinating, measuring, monitoring, controlling, and reporting – to ensure that the development and maintenance of software is systematic, disciplined, and quantified. Requirements engineering: The elicitation, analysis, specification, and validation of requirements for software
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