1,616 research outputs found
Fundamental properties of solar-like oscillating stars from frequencies of minimum : II. Model computations for different chemical compositions and mass
The large separations between the oscillation frequencies of solar-like stars
are measures of stellar mean density. The separations have been thought to be
mostly constant in the observed range of frequencies. However, detailed
investigation shows that they are not constant, and their variations are not
random but have very strong diagnostic potential for our understanding of
stellar structure and evolution. In this regard, frequencies of the minimum
large separation are very useful tools. From these frequencies, in addition to
the large separation and frequency of maximum amplitude, Y\i ld\i z et al.
recently have developed new methods to find almost all the fundamental stellar
properties. In the present study, we aim to find metallicity and helium
abundances from the frequencies, and generalize the relations given by Y\i ld\i
z et al. for a wider stellar mass range and arbitrary metallicity () and
helium abundance (). We show that the effect of metallicity is {
significant} for most of the fundamental parameters. For stellar mass, for
example, the expression must be multiplied by (Z/Z_{\sun})^{0.12}. For
arbitrary helium abundance, M \propto (Y/Y_{\sun})^{0.25} . Methods for
determination of and from pure asteroseismic quantities are based on
amplitudes (differences between maximum and minimum values of \Dnu) in the
oscillatory component in the spacing of oscillation frequencies. Additionally,
we demonstrate that the difference between the first maximum and the second
minimum is very sensitive to . It also depends on and small separation between the frequencies. Such a dependence leads us
to develop a method to find (and ) from oscillation frequencies. The
maximum difference between the estimated and model values is about 14 per
cent. It is 10 per cent for .Comment: 8 pages, 13 figures; published in MNRAS (2015
Comparison of Gaia and asteroseismic distances
Asteroseismology provides fundamental properties (mass, radius and effective
temperature) of solar-like oscillating stars using so-called scaling relations.
These properties allow the computation of the asteroseismic distance of stars.
We compare the asteroseismic distances with the recently released Gaia
distances for 74 stars studied in Y{\i}ld{\i}z et al. There is a very good
agreement between these two distances; for 64 of these stars, the difference is
less than 10 per cent. However, a systematic difference is seen if we use the
effective temperature obtained by spectroscopic methods; the Gaia distances are
about 5 per cent greater than the asteroseismic distances.Comment: 4 pages, 4 figures, accepted by MNRA
On the structure and evolution of planets and their host stars effects of various heating mechanisms on the size of giant gas planets
It is already stated in the previous studies that the radius of the giant
planets is affected by stellar irradiation. The confirmed relation between
radius and incident flux depends on planetary mass intervals. In this study, we
show that there is a single relation between radius and irradiated energy per
gram per second (), for all mass intervals. There is an extra increase in
radius of planets if is higher than 1100 times energy received by the
Earth (). This is likely due to dissociation of molecules. The tidal
interaction as a heating mechanism is also considered and found that its
maximum effect on the inflation of planets is about 15 per cent. We also
compute age and heavy element abundances from the properties of host stars,
given in the TEPCat catalogue (Southworth 2011). The metallicity given in the
literature is as [Fe/H]. However, the most abundant element is oxygen, and
there is a reverse relation between the observed abundances [Fe/H] and [O/Fe].
Therefore, we first compute [O/H] from [Fe/H] by using observed abundances, and
then find heavy element abundance from [O/H]. We also develop a new method for
age determination. Using the ages we find, we analyse variation of both radius
and mass of the planets with respect to time, and estimate the initial mass of
the planets from the relation we derive for the first time. According to our
results, the highly irradiated gas giants lose 5 per cent of their mass in
every 1 Gyr.Comment: 15 pages, 13 figures, 3 tables. Accepted by MNRA
Meristem culture for clonal micropropagation of grapevines
Experiments were carried out to determine the effects of MS medium concentrations (4/4 MS, 3/4 MS, 2/4 MS) combined with GA3 at 0.0, 0.1 and 0.5 mg/l, and vitamin formulations (MS, Morel, thiamine-inositol) on success of meristem culture and of 15 auxin (IBA) x cytokinin (BAP) combinations on shoot and root formation for clonal rnicropropagation of the wine grape cv. Kalecik Karasi and the rootstock cv. 41 B M.G. Best results were obtained from standard MS mineral composition and vitamin formulation combined with 2.5 mg/l BAP and 0.5 mg/l GA3 for primary meristem cultures of both genotypes; 0.0 mg/l IBA x 1.0 mg/l BAP for shoot subculture and 1.0 mg/l IBA x 0.0 mg/l BAP for root subculture of Kalecik Karasi; 0.0 mg/l IBA x 1.0 mg/l BAP for shoot subculture and 5.0 mg/l IBA x 0.0 mg/l BAP for root subculture of 41 B, considering shoot, explant, root, callus and particularly entire plant formation in the cultures of both stages
Crystal structure of rac-3-hydroxy-2-(p-tolyl)-2,3,3a,4,7,7a-hexahydro-1H-4,7-methanoisoindol-1-one
In the title compound, C16H17NO2, the cyclohexene ring adopts a boat conformation, and the five-membered rings have envelope conformations with the bridging atom as the flap. Their mean planes are oriented at a dihedral angle of 86.51 (7)°. The molecular structure is stabilized by a short intramolecular C - H⋯O contact. In the crystal, molecules are linked by O - H⋯O hydrogen bonds forming chains propagating along [100]. The chains are linked by C - H⋯π interactions, forming slabs parallel to (001)
An anatomical study of the origins of the medial circumflex femoral artery in the Turkish population
The medial circumflex femoral artery (MCFA) usually branches from the deep femoral
artery (DFA). It may also branch from the femoral artery (FA). In this study 100
inguinal regions of 50 cadavers were investigated. In 79 extremities (79%) MCFA
branched from DFA, while in 15 (15%) it branched from FA. In four extremities
(4%) MCFA was found to be double; in each case one of MCFAs branched from
FA and the other from DFA. In one of these four cases the lateral circumflex
femoral artery (LCFA) was also double. In one case we found a common trunk of
DFA and MCFA and in another case a common trunk of MCFA, DFA and LCFA.
Clinicians must be familiar with the variations of this clinically important artery to
improve their success in the diagnosis and treatment of pathologies in the region
Uptake of aniline and nitrobenzene from aqueous solution by organo-zeolite
Adsorption mechanisms of toxic non-ionic organic contaminants (NOCs), aniline and nitrobenzene, with natural-zeolite andorgano-zeolite (OZ) were investigated in both batch and continuous systems. In batch tests, the adsorption capacity ofaniline and nitrobenzene onto natural zeolite surface is very low or almost nil but becomes significant upon modifying thezeolite surface by hexadecyltrimethylammonium (HDTMA). A partitioning mechanism is proposed to be responsible for the
adsorption of NOCs onto OZ. The effectiveness of the partitioning mechanism is directly connected with hydrophobicproperties of the NOCs. The column tests were carried out as an indicator for continuous system. The breakthrough curveswere constructed for OZ/NOC system and the adsorption capacity of NOCs onto OZ under the present conditions weredetermined as 2.36 and 3.25 mg per gram of OZ, for aniline and nitrobenzene, respectively. A schematic model is proposedto account for the adsorption of NOCs onto OZ
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