843 research outputs found
Electronic Education at the Faculty of Nuclear Sciences and Physical Engineering
This paper deals with the current issue of electronic education, and is based on a study of Internet support for education at the Faculty of Nuclear Sciences and Physical Engineering at the Czech Technical University in Prague.The goal of the study was to establish to what extent and in what ways electronic support for education is utilized at FNSPE CTU. In order to answer these questions, a questionnaire was conducted at the faculty. We will present the outcomes here.
Reanalysis of the FEROS observations of HIP 11952
Aims. We reanalyze FEROS observations of the star HIP 11952 to reassess the
existence of the proposed planetary system. Methods. The radial velocity of the
spectra were measured by cross-correlating the observed spectrum with a
synthetic template. We also analyzed a large dataset of FEROS and HARPS
archival data of the calibrator HD 10700 spanning over more than five years. We
compared the barycentric velocities computed by the FEROS and HARPS pipelines.
Results. The barycentric correction of the FEROS-DRS pipeline was found to be
inaccurate and to introduce an artificial one-year period with a semi-amplitude
of 62 m/s. Thus the reanalysis of the FEROS data does not support the existence
of planets around HIP 11952.Comment: 7 pages, 8 figures, 1 tabl
Evolution of microstructure and mechanical properties during annealing of heavily rolled AlCoCrFeNi2. 1 eutectic high-entropy alloy
Changes in the\ua0microstructure\ua0and mechanical properties during annealing at 800\ua0\ub0C have been characterized in a 90% cold-rolled AlCoCrFeNi2.1\ua0eutectic high-entropy alloy containing the FCC and B2 (ordered BCC) phases. In the as-rolled condition, the FCC phase is found to contain a high frequency of finely spaced deformation-induced boundaries, which provides a high driving force for recrystallization within this phase. Quantitative analysis of\ua0electron backscatter diffraction\ua0data from the annealed samples indicates that recrystallization progresses faster in the FCC phase than in B2 regions. Although recrystallization leads to substantial coarsening of the microstructure, the average recrystallized grain size remains in the submicron range even after 2\ua0h at 800\ua0\ub0C. Tensile test data demonstrate that combinations of high yield strength and good ductility are obtained in partially recrystallized samples produced by annealing for 2.5â10\ua0min. However, the work-hardening capacity of each annealed sample is lower than that of the cold-rolled sample. Furthermore, for the samples annealed for at least 5\ua0min a yield drop is observed soon after the onset of\ua0plastic deformation. Analysis of the microstructure and mechanical behavior in several annealed AlCoCrFeNi2.1\ua0samples indicates a clear correlation between the magnitude of the yield drop and the recrystallized fraction. The mechanical behavior of the AlCoCrFeNi2.1\ua0alloy studied in this work is compared with that reported in previous publications
C/EBP-induced transdifferentiation reveals granulocyte-macrophage precursor-like plasticity of B cells
The lymphoid-myeloid transdifferentiation potentials of members of the C/EBP family (C/EBP{alpha}, {beta}, {delta}, and {epsilon}) were compared in v-Abl-immortalized primary B cells. Conversion of B cells to macrophages was readily induced by the ectopic expression of any C/EBP, and enhanced by endogenous C/EBP{alpha} and {beta} activation. High transgene expression of C/EBP{beta} or C/EBP{epsilon}, but not of C/EBP{alpha} or C/EBP{delta}, also induced the formation of granulocytes. Granulocytes and macrophages emerged in a mutually exclusive manner. C/EBP{beta}-expressing B cells produced granulocyte-macrophage progenitor (GMP)-like progenitors when subjected to selective pressure to eliminate lymphoid cells. The GMP-like progenitors remained self-renewing and cytokine-independent, and continuously produced macrophages and granulocytes. In addition to their suitability to study myelomonocytic lineage bifurcation, lineage-switched GMP-like progenitors could reflect the features of the lympho-myeloid lineage switch observed in leukemic progression
Planetary companions around the metal-poor star HIP 11952
Aims. We carried out a radial-velocity survey to search for planets around
metal-poor stars. In this paper we report the discovery of two planets around
HIP 11952, a metal-poor star with [Fe/H]= -1.9 that belongs to our target
sample. Methods. Radial velocity variations of HIP 11952 were monitored
systematically with FEROS at the 2.2 m telescope located at the ESO La Silla
observatory from August 2009 until January 2011. We used a cross-correlation
technique to measure the stellar radial velocities (RV). Results. We detected a
long-period RV variation of 290 d and a short-period one of 6.95 d. The
spectroscopic analysis of the stellar activity reveals a stellar rotation
period of 4.8 d. The Hipparcos photometry data shows intra-day variabilities,
which give evidence for stellar pulsations. Based on our analysis, the observed
RV variations are most likely caused by the presence of unseen planetary
companions. Assuming a primary mass of 0.83 M\odot, we computed minimum
planetary masses of 0.78 MJup for the inner and 2.93 MJup for the outer planet.
The semi-major axes are a1 = 0.07 AU and a2 = 0.81 AU, respectively.
Conclusions. HIP 11952 is one of very few stars with [Fe/H]< -1.0 which have
planetary companions. This discovery is important to understand planet
formation around metal-poor starsComment: Published in A&
On the diffraction pattern of C60 peapods
We present detailed calculations of the diffraction pattern of a powder of
bundles of C peapods. The influence of all pertinent structural
parameters of the bundles on the diffraction diagram is discussed, which should
lead to a better interpretation of X-ray and neutron diffraction diagrams. We
illustrate our formalism for X-ray scattering experiments performed on peapod
samples synthesized from 2 different technics, which present different
structural parameters. We propose and test different criteria to solve the
difficult problem of the filling rate determination.Comment: Sumitted 19 May 200
Analysis of Peculiarities of the Stellar Velocity Field in the Solar Neighborhood
Based on a new version of the Hipparcos catalogue and an updated
Geneva-Copenhagen survey of F and G dwarfs, we analyze the space velocity field
of about 17000 single stars in the solar neighborhood. The main known clumps,
streams, and branches (Pleiades, Hyades, Sirius, Coma Berenices, Hercules, Wolf
630-alpha Ceti, and Arcturus) have been identified using various approaches.
The evolution of the space velocity field for F and G dwarfs has been traced as
a function of the stellar age. We have managed to confirm the existence of the
recently discovered KFR08 stream. We have found 19 Hipparcos stars, candidates
for membership in the KFR08 stream, and obtained an isochrone age estimate for
the stream, 13 Gyr. The mean stellar ages of the Wolf 630-alpha Ceti and
Hercules streams are shown to be comparable, 4--6 Gyr. No significant
differences in the metallicities of stars belonging to these streams have been
found. This is an argument for the hypothesis that these streams owe their
origin to a common mechanism.Comment: 23 pages, 9 figure
Quantifying Kinematic Substructure in the Milky Way's Stellar Halo
We present and analyze the positions, distances, and radial velocities for
over 4000 blue horizontal-branch (BHB) stars in the Milky Way's halo, drawn
from SDSS DR8. We search for position-velocity substructure in these data, a
signature of the hierarchical assembly of the stellar halo. Using a cumulative
"close pair distribution" (CPD) as a statistic in the 4-dimensional space of
sky position, distance, and velocity, we quantify the presence of
position-velocity substructure at high statistical significance among the BHB
stars: pairs of BHB stars that are close in position on the sky tend to have
more similar distances and radial velocities compared to a random sampling of
these overall distributions. We make analogous mock-observations of 11
numerical halo formation simulations, in which the stellar halo is entirely
composed of disrupted satellite debris, and find a level of substructure
comparable to that seen in the actually observed BHB star sample. This result
quantitatively confirms the hierarchical build-up of the stellar halo through a
signature in phase (position-velocity) space. In detail, the structure present
in the BHB stars is somewhat less prominent than that seen in most simulated
halos, quite possibly because BHB stars represent an older sub-population. BHB
stars located beyond 20 kpc from the Galactic center exhibit stronger
substructure than at kpc.Comment: 29 page, 10 figures, 1 table; accepted by APJ; for related article by
another group see arXiv:1011.192
Annotations for Rule-Based Models
The chapter reviews the syntax to store machine-readable annotations and
describes the mapping between rule-based modelling entities (e.g., agents and
rules) and these annotations. In particular, we review an annotation framework
and the associated guidelines for annotating rule-based models of molecular
interactions, encoded in the commonly used Kappa and BioNetGen languages, and
present prototypes that can be used to extract and query the annotations. An
ontology is used to annotate models and facilitate their description
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