130 research outputs found
Место и роль ценностей в механизме социализации
В статье рассматривается специфика механизма социализации и проблема ценностных ориентаций в условиях социокультурных трансформаций украинского общества. Определяются ценностные ориентиры гражданского общества как приоритетного для Украины.У статті розглядається специфика механізму соціалізації і проблема цінностних орієнтацій в умовах соціокультурних трансформацій українського суспільства. Визначаються цінностні орієнтири громадянського суспільства як приоритетного для України.The article deals with peculiarities of socialization and the problem of value ori-entation under the conditions of socio-cultural transformations of the Ukrainian society. We also define value orientation of the civil society as optimal for Ukraine
Metallicities for 13 nearby open clusters from high-resolution spectroscopy of dwarf and giant stars. Stellar metallicity, stellar mass, and giant planets
We present a study of accurate stellar parameters and iron abundances for 39
giants and 16 dwarfs in the 13 open clusters IC2714, IC4651, IC4756, NGC2360,
NGC2423, NGC2447 (M93), NGC2539, NGC2682 (M67), NGC3114, NGC3680, NGC4349,
NGC5822, NGC6633. The analysis was done using a set of high-resolution and
high-S/N spectra obtained with the UVES spectrograph (VLT). These clusters are
currently being searched for planets using precise radial velocities. For all
the clusters, the derived average metallicities are close to solar.
Interestingly, the values derived seem to depend on the line-list used. This
dependence and its implications for the study of chemical abundances in giants
stars are discussed. We show that a careful choice of the lines may be crucial
for the derivation of metallicities for giant stars on the same metallicity
scale as those derived for dwarfs. Finally, we discuss the implications of the
derived abundances for the metallicity- and mass-giant planet correlation. We
conclude that a good knowledge of the two parameters is necessary to correctly
disentangle their influence on the formation of giant planets.Comment: accepted for publication in A&
Molecular characterization of a conserved archaeal copper resistance (cop) gene cluster and its copper-responsive regulator in Sulfolobus solfataricus P2
Using a comparative genomics approach, a copper resistance gene cluster has been identified in multiple archaeal genomes. The cop cluster is predicted to encode a metallochaperone (CopM), a P-type copper-exporting ATPase (CopA) and a novel, archaea-specific transcriptional regulator (CopT) which might control the expression of the cop genes. Sequence analysis revealed that CopT has an N-terminal DNA-binding helix-turn-helix domain and a C-terminal TRASH domain; TRASH is a novel domain which has recently been proposed to be uniquely involved in metal-binding in sensors, transporters and trafficking proteins in prokaryotes. The present study describes the molecular characterization of the cop gene cluster in the thermoacidophilic crenarchaeon Sulfolobus solfataricus. The polycistronic copMA transcript was found to accumulate in response to growth-inhibiting copper concentrations, whereas copT transcript abundance appeared to be constitutive. DNA-binding assays revealed that CopT binds to the copMA promoter at multiple sites, both upstream and downstream of the predicted TATA-BRE site. Copper was found to specifically modulate the affinity of DNA binding by CopT. This study describes a copper-responsive operon in archaea, a new family of archaeal DNA-binding proteins, and supports the idea that this domain plays a prominent role in the archaeal copper response. A model is proposed for copper-responsive transcriptional regulation of the copMA gene cluste
Orbital migration and the period distribution of exoplanets
We use the model for the migration of planets introduced in Del Popolo,
Yesilyurt & Ercan (2003) to calculate the observed mass and semimajor axis
distribution of extra-solar planets. The assumption that the surface density in
planetesimals is proportional to that of gas is relaxed, and in order to
describe disc evolution we use a method which, using a series of simplifying
assumptions, is able to simultaneously follow the evolution of gas and solid
particles for up to . The distribution of planetesimals obtained
after is used to study the migration rate of a giant planet
through the model of this paper. The disk and migration models are used to
calculate the distribution of planets as function of mass and semimajor axis.
The results show that the model can give a reasonable prediction of planets'
semi-major axes and mass distribution. In particular there is a pile-up of
planets at AU, a minimum near 0.3 AU, indicating a paucity of
planets at that distance, and a rise for semi-major axes larger than 0.3 AU,
out to 3 AU. The semi-major axis distribution shows that the more massive
planets (typically, masses larger than ) form preferentially in
the outer regions and do not migrate much. Intermediate-mass objects migrate
more easily whatever the distance they form, and that the lighter planets
(masses from sub-Saturnian to Jovian) migrate easily.Comment: published in A&
The structure of cool accretion disc in semidetached binaries
We present the results of qualitative consideration of possible changes
occurring during the transition from the hot accretion disc to the cool one. We
argue the possible existence of one more type of spiral density waves in the
inner part of the disc where gasdynamical perturbations are negligible. The
mechanism of formation of such a wave as well as its parameters are considered.
We also present the results of 3D gasdynamical simulation of cool accretion
discs. These results confirm the hypothesis of possible formation of the spiral
wave of a new, "precessional" type in the inner regions of the disc. Possible
observational manifestations of this wave are discussed.Comment: LaTeX, 16 pages, 8 figures, to be published in Astron. Z
Identification of distinct steps during tubule formation by the movement of protein of Cowpea mosaic virus
The movement protein (MP) of Cowpea mosaic virus (CPMV) forms tubules through plasmodesmata in infected plants thus enabling virus particles to move from cell to cell. Localization studies of mutant MPs fused to GFP in protoplasts and plants identified several functional domains within the MP that are involved in distinct steps during tubule formation. Coinoculation experiments and the observation that one of the C-terminal deletion mutants accumulated uniformly in the plasma membrane suggest that dimeric or multimeric MP is first targeted to the plasma membrane. At the plasma membrane the MP quickly accumulates in peripheral punctuate spots, from which tubule formation is initiated. One of the mutant MPs formed tubules containing virus particles on protoplasts, but could not support cell-to-cell movement in plants. The observations that this mutant MP accumulated to a higher level in the cell than wt MP and did not accumulate in the cell wall opposite infected cells suggest that breakdown or disassembly of tubules in neighbouring, uninfected cells is required for cell-to-cell movement
Habitable Zones in the Universe
Habitability varies dramatically with location and time in the universe. This
was recognized centuries ago, but it was only in the last few decades that
astronomers began to systematize the study of habitability. The introduction of
the concept of the habitable zone was key to progress in this area. The
habitable zone concept was first applied to the space around a star, now called
the Circumstellar Habitable Zone. Recently, other, vastly broader, habitable
zones have been proposed. We review the historical development of the concept
of habitable zones and the present state of the research. We also suggest ways
to make progress on each of the habitable zones and to unify them into a single
concept encompassing the entire universe.Comment: 71 pages, 3 figures, 1 table; to be published in Origins of Life and
Evolution of Biospheres; table slightly revise
Planetary population synthesis
In stellar astrophysics, the technique of population synthesis has been
successfully used for several decades. For planets, it is in contrast still a
young method which only became important in recent years because of the rapid
increase of the number of known extrasolar planets, and the associated growth
of statistical observational constraints. With planetary population synthesis,
the theory of planet formation and evolution can be put to the test against
these constraints. In this review of planetary population synthesis, we first
briefly list key observational constraints. Then, the work flow in the method
and its two main components are presented, namely global end-to-end models that
predict planetary system properties directly from protoplanetary disk
properties and probability distributions for these initial conditions. An
overview of various population synthesis models in the literature is given. The
sub-models for the physical processes considered in global models are
described: the evolution of the protoplanetary disk, the planets' accretion of
solids and gas, orbital migration, and N-body interactions among concurrently
growing protoplanets. Next, typical population synthesis results are
illustrated in the form of new syntheses obtained with the latest generation of
the Bern model. Planetary formation tracks, the distribution of planets in the
mass-distance and radius-distance plane, the planetary mass function, and the
distributions of planetary radii, semimajor axes, and luminosities are shown,
linked to underlying physical processes, and compared with their observational
counterparts. We finish by highlighting the most important predictions made by
population synthesis models and discuss the lessons learned from these
predictions - both those later observationally confirmed and those rejected.Comment: 47 pages, 12 figures. Invited review accepted for publication in the
'Handbook of Exoplanets', planet formation section, section editor: Ralph
Pudritz, Springer reference works, Juan Antonio Belmonte and Hans Deeg, Ed
Planet Populations as a Function of Stellar Properties
Exoplanets around different types of stars provide a window into the diverse
environments in which planets form. This chapter describes the observed
relations between exoplanet populations and stellar properties and how they
connect to planet formation in protoplanetary disks. Giant planets occur more
frequently around more metal-rich and more massive stars. These findings
support the core accretion theory of planet formation, in which the cores of
giant planets form more rapidly in more metal-rich and more massive
protoplanetary disks. Smaller planets, those with sizes roughly between Earth
and Neptune, exhibit different scaling relations with stellar properties. These
planets are found around stars with a wide range of metallicities and occur
more frequently around lower mass stars. This indicates that planet formation
takes place in a wide range of environments, yet it is not clear why planets
form more efficiently around low mass stars. Going forward, exoplanet surveys
targeting M dwarfs will characterize the exoplanet population around the lowest
mass stars. In combination with ongoing stellar characterization, this will
help us understand the formation of planets in a large range of environments.Comment: Accepted for Publication in the Handbook of Exoplanet
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