719 research outputs found
Six questions on the construction of ontologies in biomedicine
(Report assembled for the Workshop of the AMIA Working Group on Formal Biomedical Knowledge Representation in connection with AMIA Symposium, Washington DC, 2005.)
Best practices in ontology building for biomedicine have been frequently discussed in recent years. However there is a range of seemingly disparate views represented by experts in the field. These views not only reflect the different uses to which ontologies are put, but also the experiences and disciplinary background of these experts themselves. We asked six questions related to biomedical ontologies to what we believe is a representative sample of ontologists in the biomedical field and came to a number conclusions which we believe can help provide an insight into the practical problems which ontology builders face today
Measurement of the energy resolution and calibration of hybrid pixel detectors with GaAs:Cr sensor and Timepix readout chip
This paper describes an iterative method of per-pixel energy calibration of
hybrid pixel detectors with GaAs:Cr sensor and Timepix readout chip. A
convolution of precisely measured spectra of characteristic X-rays of different
metals with the resolution and the efficiency of the pixel detector is used for
the calibration. The energy resolution of the detector is also measured during
the calibration. The use of per-pixel calibration allows to achieve a good
energy resolution of the Timepix detector with GaAs:Cr sensor: 8% and 13% at 60
keV and 20 keV, respectively
Validation of Advanced Computer Codes for VVER Technology: LB-LOCA Transient in PSB-VVER Facility
The OECD/NEA PSB-VVER project provided unique and useful experimental data for code validation from PSB-VVER test facility. This facility represents the scaled-down layout of the Russian-designed pressurized water reactor, namely, VVER-1000. Five experiments were executed, dealing with loss of coolant scenarios (small, intermediate, and large break loss of coolant accidents), a primary-to-secondary leak, and a parametric study (natural circulation test) aimed at characterizing the VVER system at reduced mass inventory conditions. The comparative analysis, presented in the paper, regards the large break loss of coolant accident experiment. Four participants from three different institutions were involved in the benchmark and applied their own models and set up for four different thermal-hydraulic system codes. The benchmark demonstrated the performances of such codes in predicting phenomena relevant for safety on the basis of fixed criteria
The first evidence for multiple pulsation axes: a new roAp star in the Kepler field, KIC 10195926
We have discovered a new rapidly oscillating Ap star among the Kepler Mission
target stars, KIC 10195926. This star shows two pulsation modes with periods
that are amongst the longest known for roAp stars at 17.1 min and 18.1 min,
indicating that the star is near the terminal age main sequence. The principal
pulsation mode is an oblique dipole mode that shows a rotationally split
frequency septuplet that provides information on the geometry of the mode. The
secondary mode also appears to be a dipole mode with a rotationally split
triplet, but we are able to show within the improved oblique pulsator model
that these two modes cannot have the same axis of pulsation. This is the first
time for any pulsating star that evidence has been found for separate pulsation
axes for different modes. The two modes are separated in frequency by 55
microHz, which we model as the large separation. The star is an alpha^2 CVn
spotted magnetic variable that shows a complex rotational light variation with
a period of Prot = 5.68459 d. For the first time for any spotted magnetic star
of the upper main sequence, we find clear evidence of light variation with a
period of twice the rotation period; i.e. a subharmonic frequency of . We propose that this and other subharmonics are the first observed
manifestation of torsional modes in an roAp star. From high resolution spectra
we determine Teff = 7400 K, log g = 3.6 and v sin i = 21 km/s. We have found a
magnetic pulsation model with fundamental parameters close to these values that
reproduces the rotational variations of the two obliquely pulsating modes with
different pulsation axes. The star shows overabundances of the rare earth
elements, but these are not as extreme as most other roAp stars. The spectrum
is variable with rotation, indicating surface abundance patches.Comment: 17 pages; 16 figures; MNRA
On certain other sets of integers
We show that if A is a subset of {1,...,N} containing no non-trivial
three-term arithmetic progressions then |A|=O(N/ log^{3/4-o(1)} N).Comment: 29 pp. Corrected typos. Added definitions for some non-standard
notation and remarks on lower bound
Psychological features of hockey players with different stress resistance
Objective: to study emotional and characterological features of hockey players with different stress resistance. Materials and methods: 120 hockey players of the Junior Hockey League (JHL) aged from 16 to 21 years were involved in the study. Interviewing, evaluation of medical records, test of differential self-assessment of the functional state (SAN) and method of personality research using the questionnaire FPI (modified form B) were conducted. Results: according to the results of the study, it was found that hockey players with high stress resistance had significantly lower rates on the scales of neuroticism, depression, irritability, emotional lability, as well as significantly higher rates on the scales of sociability, openness, well-being and mood (p<0.05). On the contrary, hockey players with low stress resistance had opposite features. Also, hockey players with high stress resistance had a higher sports experience, as well as better health. Conclusions: stress-resistance of players has significantly high connection with neurotism and irritability, as well as significant moderate negative association with age and sports experience. It is established that with increasing of neuroticism and irritability, as well as reducing of the age and sports experience stress resistance of hockey players decreases. Taking into account the results of the study, in order to maintain health, prolong professional longevity and maintain the proper level of performance of hockey players, it is important to use an integrated approach that provides a whole group of activities: rationalization of work and rest, improvement of working conditions, optimization of microclimate in the team
Pulsation in the atmosphere of the roAp star HD 24712. I. Spectroscopic observations and radial velocity measurements
We have investigated the structure of the pulsating atmosphere of one of the
best studied rapidly oscillating Ap stars, HD 24712. For this purpose we
analyzed spectra collected during 2001-2004. An extensive data set was obtained
in 2004 simultaneously with the photometry of the Canadian MOST mini-satellite.
This allows us to connect directly atmospheric dynamics observed as radial
velocity variations with light variations seen in photometry. We directly
derived for the first time and for different chemical elements, respectively
ions, phase shifts between photometric and radial velocity pulsation maxima
indicating, as we suggest, different line formation depths in the atmosphere.
This allowed us to estimate for the first time the propagation velocity of a
pulsation wave in the outer stellar atmosphere of a roAp star to be slightly
lower than the sound speed. We confirm large pulsation amplitudes (150-400 m/s)
for REE lines and the Halpha core, while spectral lines of the other elements
(Mg, Si, Ca, and Fe-peak elements) have nearly constant velocities. We did not
find different pulsation amplitudes and phases for the lines of rare-earth
elements before and after the Balmer jump, which supports the hypothesis of REE
concentration in the upper atmosphere above the hydrogen line-forming layers.
We also discuss radial velocity amplitudes and phases measured for individual
spectral lines as tools for a 3D tomography of the atmosphere of HD 24712.Comment: accepted by A&
A search for kilogauss magnetic fields in white dwarfs and hot subdwarf stars
We present new results of a survey for weak magnetic fields among DA white
dwarfs with inclusion of some brighter hot subdwarf stars. We have detected
variable circular polarization in the Halpha line of the hot subdwarf star
Feige 34 (SP: sdO). From these data, we estimate that the longitudinal magnetic
field of this star varies from -1.1 +/- 3.2 kG to +9.6 +/- 2.6 kG, with a mean
of about +5 kG and a period longer than 2 h. In this study, we also confirm the
magnetic nature of white dwarf WD1105-048 and present upper limits of kilogauss
longitudinal magnetic fields of 5 brightest DA white dwarfs. Our data support
recent finding that 25% of white dwarfs have kilogauss magnetic fields. This
frequency also confirms results of early estimates obtained using the magnetic
field function of white dwarfs.Comment: accepted for publication in the Astrphysical Journa
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