85 research outputs found
Surface temperature and synthetic spectral energy distributions for rotationally deformed stars
The spectral energy distribution (SED) of a non-spherical star could differ
significantly from the SED of a spherical star with the same average
temperature and luminosity. Calculation of the SED of a deformed star is often
approximated as a composite of several spectra, each produced by a plane
parallel model of given effective temperature and gravity. The weighting of
these spectra over the stellar surface, and hence the inferred effective
temperature and luminosity, will be dependent on the inclination of the
rotation axis of the star with respect to the observer, as well as the
temperature and gravity distribution on the stellar surface. Here we calculate
the surface conditions of rapidly rotating stars with a 2D stellar structure
and evolution code and compare the effective temperature distribution to that
predicted by von Zeipel's law. We calculate the composite spectrum for a
deformed star by interpolating within a grid of intensity spectra of plane
parallel model atmospheres and integrating over the surface of the star. Using
this method, we find that the deduced variation of effective temperature with
inclination can be as much as 3000 K for an early B star, depending on the
details of the underlying model.Comment: 38 pages, 9 figures (AAStex preprint format). Accepted for
publication in the Ap
A NLTE line blanketed model of a solar type star
We present LTE and NLTE atmospheric models of a star with solar parameters,
and study the effect of treating many thousands of Iron group lines out of LTE
on the computed atmospheric structure, overall absolute flux distribution, and
the moderately high resolution spectrum in the visible and near UV bands. Our
NLTE modeling includes the first two or three ionization stages of 20 chemical
elements, up to and including much of the Fe-group, and includes about 20000 Fe
I and II lines. We investigate separately the effects of treating the light
metals and the Fe-group elements in NLTE. Our main conclusions are that 1) NLTE
line blanketed models with direct multi-level NLTE for many actual transitions
gives qualitatively similar results as the more approximate treatment of
Anderson (1989) for both the Fe statistical equilibrium and the atmospheric
temperature structure, 2) models with many Fe lines in NLTE have a temperature
structure that agrees more closely with LTE semi-empirical models based on
center-to-limb variation and a wide variety of spectra lines, whereas LTE
models agree more with semi-empirical models based only on an LTE calculation
of the Fe I excitation equilibrium, 3) the NLTE effects of Fe-group elements on
the model structure and flux distribution are much more important than the NLTE
effects of all the light metals combined, and serve to substantially increases
the violet and near UV flux level as a result of NLTE Fe over-ionization. These
results suggest that there may still be important UV opacity missing from the
models.Comment: Accepted for publication in The Astrophysical Journa
Numerical Simulations of Magnetoacoustic-Gravity Waves in the Solar Atmosphere
We investigate the excitation of magnetoacoustic-gravity waves generated from
localized pulses in the gas pressure as well as in vertical component of
velocity. These pulses are initially launched at the top of the solar
photosphere that is permeated by a weak magnetic field. We investigate three
different configurations of the background magnetic field lines: horizontal,
vertical and oblique to the gravitational force. We numerically model
magnetoacoustic-gravity waves by implementing a realistic (VAL-C) model of
solar temperature. We solve two-dimensional ideal magnetohydrodynamic equations
numerically with the use of the FLASH code to simulate the dynamics of the
lower solar atmosphere. The initial pulses result in shocks at higher
altitudes. Our numerical simulations reveal that a small-amplitude initial
pulse can produce magnetoacoustic-gravity waves, which are later reflected from
the transition region due to the large temperature gradient. The atmospheric
cavities in the lower solar atmosphere are found to be the ideal places that
may act as a resonator for various oscillations, including their trapping and
leakage into the higher atmosphere. Our numerical simulations successfully
model the excitation of such wave modes, their reflection and trapping, as well
as the associated plasma dynamics
КОМП’ЮТЕРНО-ІНФОРМАЦІЙНИЙ МОНІТОРИНГ ЗАХВОРЮВАНОСТІ НА ТУБЕРКУЛЬОЗ ПРИ ВІДНОСНІЙ СТАБІЛІЗАЦІЇ ЕПІДЕМІЇ
Ґрунтуючись на цифрових комп’ютерно-інформаційних технологіях спостереження, проведено вибіркову оцінку захворюваності на туберкульоз у різних вікових категоріях населення. З цією метою використані щорічні форми звітних матеріалів, передбачених МОЗ України, результати власних спостережень і дані банківського накопичення інформації в системі “MS EXCEL”. Вихідні позиції формувалися з врахуванням епідпоказників по Україні та Львівській області за десятирічний період спостереження (2000–2009 рр.), який у зв’язку з різними висхідними характеристиками був розділений на перший етап (2000–2004 рр.), що засвідчував прогресуюче погіршення епідситуації з туберкульозу, та другий етап (2005–2009 рр.), при якому констатували відносну стабілізацію захворюваності. Результати опрацювали з використанням статистичних і математичних функцій програми “MS EXCEL”, параметричних і непараметричних характеристик для встановлення кореляційного зв’язку при оцінці динаміки епідеміологічних показників. Отримані дані досліджень серед загальної популяції населення дозволили стверджувати, що за рівнем середній показник захворюваності на туберкульоз в Україні значно перевищував такий у Львівській області незалежно від вікового цензу населення. Разом з тим, захворюваність у вогнищах туберкульозної інфекції свідчила про зростання даного показника у Львівській області як у дитячому, підлітковому віці, так і в дорослих, що обґрунтовувало більш якісну реалізацію лікувально-профілактичних заходів.
The impact of non-LTE effects and granulation inhomogeneities on the derived iron and oxygen abundances in metal-poor halo stars
This paper presents the results of a detailed theoretical investigation of
the impact of non-LTE effects and of granulation inhomogeneities on the derived
iron and oxygen abundances in the metal-poor halo subgiant HD140283. Our
analysis is based on both the `classical' one-dimensional (1D) stellar
atmosphere models and on the new generation of three-dimensional (3D)
hydrodynamical models. We find that the non-LTE effects on the iron abundance
derived from Fe {\sc i} lines are very important, amounting to dex
and to dex in the 3D and 1D cases, respectively. On the other hand,
we find that non-LTE and 3D effects have to be taken into account for a
reliable determination of the iron abundance from weak Fe {\sc ii} lines,
because the significant overexcitation of their upper levels in the granular
regions tend to produce emission features. As a result such Fe {\sc ii} lines
are weaker than in LTE and the abundance correction amounts to dex
for the 3D case. We derive also the oxygen-to-iron abundance ratio in the
metal-poor star HD140283 by using the O {\sc i} triplet at 7772--5 \AA and the
forbidden [O {\sc i}] line at 6300 \AA. Interestingly, when both non-LTE and 3D
effects are taken into account there still remains significant discrepancies in
the iron abundances derived from Fe {\sc i} and Fe {\sc ii} lines, as well as
in the oxygen abundances inferred from the O {\sc i} and [O {\sc i}] lines. We
conclude that the metalicity of this type of metal-poor stars could be
significantly larger than previously thought, which may have far-reaching
implications in stellar astrophysics.Comment: The Astrophysical Journal (in press). (35 pages, 5 figures and 4
tables
Permitted Oxygen Abundances and the Temperature Scale of Metal-Poor Turn-Off Stars
We use high quality VLT/UVES published data of the permitted OI triplet and
FeII lines to determine oxygen and iron abundances in unevolved (dwarfs,
turn-off, subgiants) metal-poor halo stars. The calculations have been
performed both in LTE and NLTE, employing effective temperatures obtained with
the new infrared flux method (IRFM) temperature scale by Ramirez & Melendez,
and surface gravities from Hipparcos parallaxes and theoretical isochrones. A
new list of accurate transition probabilities for FeII lines, tied to the
absolute scale defined by laboratory measurements, has been used. We find a
plateau in the oxygen-to-iron ratio over more than two orders of magnitude in
iron abundance (-3.2 < [Fe/H] < -0.7), with a mean [O/Fe] = 0.5 dex (sigma =
0.1 dex), independent of metallicity, temperature and surface gravity.
According to the new IRFM Teff scale, the temperatures of turn-off halo stars
strongly depend on metallicity, a result that is in excellent qualitative and
quantitative agreement with stellar evolution calculations, which predict that
the Teff of the turn-off at [Fe/H] = -3 is about 600-700 K higher than that at
[Fe/H] = -1.Comment: In press, Ap
Oxygen in the Very Early Galaxy
Oxygen abundances in a sample of ultra-metal-poor subdwarfs have been derived
from measurements of the oxygen triplet at 7771--5 A and OH lines in the near
UV performed in high-resolution and high signal-to-noise spectra obtained with
WHT/UES, KeckI/HIRES, and VLT/UVES. Our Fe abundances were derived in LTE and
then corrected for NLTE effects following Thevenin and Idiart (1999). The new
oxygen abundances confirm previous findings for a progressive linear rise in
the oxygen-to-iron ratio with a slope -0.33+-0.02 from solar metallicity to
[Fe/H] -3. A slightly higher slope would be obtained if the Fe NLTE corrections
were not considered. Below [Fe/H]= -2.5 our stars show [O/Fe] ratios as high as
~ 1.17 (G64-12), which can be interpreted as evidence for oxygen overproduction
in the very early epoch of the formation of the halo, possibly associated with
supernova events with very massive progenitor stars. We show that the arguments
against this linear trend given by Fulbright and Kraft (1999), based on the LTE
Fe analysis of two metal-poor stars cannot be sustained when an NLTE analysis
is performed. Using 1-D models our analysis of three oxygen indicators
available for BD +23 3130 gives consistent abundances within 0.16 dex and
average [O/Fe] ratio of 0.91.Comment: 45 pages, 11 figures, accepted for publication in The Astrophysical
Journa
Differences sustained between diffuse and limited forms of juvenile systemic sclerosis in expanded international cohort. www.juvenile-scleroderma.com
OBJECTIVES: To evaluate the baseline clinical characteristics of juvenile systemic sclerosis (jSSc) patients in the international Juvenile SSc Inception Cohort (jSScC), compare these characteristics between the classically defined diffuse (dcjSSc) and limited cutaneous (lcjSSc) subtypes, and among those with overlap features. METHODS: A cross-sectional study was performed using baseline visit data. Demographic, organ system evaluation, treatment, and patient and physician reported outcomes were extracted and summary statistics applied. Comparisons between dcjSSc and lcSSc subtypes and patients with and without overlap features were performed using Chi-square and Mann Whitney U-tests. RESULTS: At data extraction 150 jSSc patients were enrolled across 42 centers, 83% were Caucasian, 80% female, dcjSSc predominated (72%), and 17% of the cohort had overlap features. Significant differences were found between dcjSSc and lcjSSc regarding the modified Rodnan Skin Score, presence of Gottron's papules, digital tip ulceration, 6 Minute walk test, composite pulmonary and cardiac involvement. All more frequent in dcSSc except for cardiac involvement. DcjSSc patients had significantly worse scores for physician rated disease activity and damage. A significantly higher occurrence of Gottron's papules, musculoskeletal involvement and composite pulmonary involvement, and significantly lower frequency of Raynaud's phenomenon, were seen in those with overlap features. CONCLUSION: Results from a large international jSSc cohort demonstrate significant differences between dcjSSc and lcjSSc patients including more globally severe disease and increased frequency of ILD in dcjSSc patients, while those with lcSSc have more frequent cardiac involvement. Those with overlap features had an unexpected higher frequency of interstitial lung disease
Defining criteria for disease activity states in systemic juvenile idiopathic arthritis based on the systemic Juvenile Arthritis Disease Activity Score
Objective
To develop and validate cutoff values in the systemic Juvenile Arthritis Disease Activity Score 10 (sJADAS10) that distinguish the states of inactive disease (ID), minimal disease activity (MiDA), moderate disease activity (MoDA), and high disease activity (HDA) in children with systemic juvenile idiopathic arthritis (sJIA), based on subjective disease state assessment by the treating pediatric rheumatologist.
Methods
The cutoffs definition cohort was composed of 400 patients enrolled at 30 pediatric rheumatology centers in 11 countries. Using the subjective physician rating as an external criterion, 6 methods were applied to identify the cutoffs: mapping, calculation of percentiles of cumulative score distribution, Youden index, 90% specificity, maximum agreement, and ROC curve analysis. Sixty percent of the patients were assigned to the definition cohort and 40% to the validation cohort. Cutoff validation was conducted by assessing discriminative ability.
Results
The sJADAS10 cutoffs that separated ID from MiDA, MiDA from MoDA, and MoDA from HDA were ≤ 2.9, ≤ 10, and > 20.6. The cutoffs discriminated strongly among different levels of pain, between patients with or without morning stiffness, and between patients whose parents judged their disease status as remission or persistent activity/flare or were satisfied or not satisfied with current illness outcome.
Conclusion
The sJADAS cutoffs revealed good metrologic properties in both definition and validation cohorts, and are therefore suitable for use in clinical trials and routine practice
NLRP12 -ассоциированный периодический синдром: описание собственного наблюдения и анализ данных литературы
Autoinflammatory diseases (AIDs) are a group of rare disorders characterized by persistent or recurrent inflammation caused by the hyperactivation of mediators and innate immune cells (neutrophils, monocytes/macrophages). The paper describes the authors' own case of NLRP12-associated AIDs and the efficiency of canakinumab therapy and reviews a series of cases of the similar disease, which are given in the literature. Аутовоспалительные заболевания (АВЗ) – это группа редких заболеваний, характеризующихся персистирующим или возвратным воспалением, обусловленным гиперактивацией медиаторов и клеток врожденного иммунитета (нейтрофилов, моноцитов/макрофагов). В статье приводятся описание собственного наблюдения NLRP12-ассоциированного АВЗ, эффективности терапии канакинумабом, а также обзор серии случаев аналогичного заболевания, представленных в литературе.
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