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In the era of precision cosmology, it is essential to determine the Hubble constant empirically with an accuracy of one per cent or better 1 . At present, the uncertainty on this constant is dominated by the uncertainty in the calibration of the Cepheid period–luminosity relationship 2 , 3 (also known as the Leavitt law). The Large Magellanic Cloud has traditionally served as the best galaxy with which to calibrate Cepheid period–luminosity relations, and as a result has become the best anchor point for the cosmic distance scale 4 , 5 . Eclipsing binary systems composed of late-type stars offer the most precise and accurate way to measure the distance to the Large Magellanic Cloud. Currently the limit of the precision attainable with this technique is about two per cent, and is set by the precision of the existing calibrations of the surface brightness–colour relation 5 , 6 . Here we report a calibration of the surface brightness–colour relation with a precision of 0.8 per cent. We use this calibration to determine a geometrical distance to the Large Magellanic Cloud that is precise to 1 per cent based on 20 eclipsing binary systems. The final distance is 49.59 ± 0.09 (statistical) ± 0.54 (systematic) kiloparsecs. A new calibration of the surface brightness–colour relation of eclipsing binary stars gives a distance to the Large Magellanic Cloud that is precise to one per cent.

Observations of eight long-period, late-type eclipsing-binary systems composed of cool, giant stars are used to determine a distance to the Large Magellanic Cloud accurate to 2.2 per cent, providing a base for a determination of the Hubble constant to an accuracy of 3 per cent. Accurate distance to our nearest-neighbour galaxy The physical properties of stars in eclipsing binary systems can be accurately determined thanks to the intimate interactions between the two bodies, and by monitoring the fluctuating light from such systems it is possible to obtain accurate extragalactic distance measurement. This technique has now been used to determine the most accurate distance estimate yet for the Large Magellanic Cloud (LMC), our nearest-neighbour galaxy. The data from eight long-period, late-type eclipsing systems particularly suitable for this calibration technique suggest that the LMC is around 49.97 kiloparsecs from us, to an accuracy of 2.2%. The distance to the LMC is a key element in determining the Hubble constant, an important measure of the rate of expansion of the Universe. In the era of precision cosmology, it is essential to determine the Hubble constant to an accuracy of three per cent or better 1 , 2 . At present, its uncertainty is dominated by the uncertainty in the distance to the Large Magellanic Cloud (LMC), which, being our second-closest galaxy, serves as the best anchor point for the cosmic distance scale 2 , 3 . Observations of eclipsing binaries offer a unique opportunity to measure stellar parameters and distances precisely and accurately 4 , 5 . The eclipsing-binary method was previously applied to the LMC 6 , 7 , but the accuracy of the distance results was lessened by the need to model the bright, early-type systems used in those studies. Here we report determinations of the distances to eight long-period, late-type eclipsing systems in the LMC, composed of cool, giant stars. For these systems, we can accurately measure both the linear and the angular sizes of their components and avoid the most important problems related to the hot, early-type systems. The LMC distance that we derive from these systems (49.97 ± 0.19 (statistical) ± 1.11 (systematic) kiloparsecs) is accurate to 2.2 per cent and provides a firm base for a 3-per-cent determination of the Hubble constant, with prospects for improvement to 2 per cent in the future.

Cepheid variable mass Cepheid variable stars have been important in the development of modern astrophysics through their use in establishing cosmic distances, but despite extensive research they retain some of their mysteries. One is the mass discrepancy problem, the fact that the masses of classical Cepheid supergiants calculated from pulsation theory (it is pulsation that causes their luminosity to vary) are smaller than the masses calculated from stellar evolution models. The ideal system in which to make an accurate mass determination would be a well-detached double-lined eclipsing binary in which one of the components was a classical Cepheid. Pietrzynski et al . report the discovery of just such a system in the Large Magellanic Cloud. The resultant mass determination, to a precision of one per cent, is in agreement with the mass as predicted by pulsation theory. Masses of pulsating classical Cepheid supergiants derived from stellar pulsation theory are smaller than the masses derived from stellar evolution theory. An independent determination for a classical Cepheid in a binary system is needed to determine which is correct. These authors report the discovery of a classical Cepheid in the Large Magellanic Cloud. They determine the mass to a precision of one per cent and show that it agrees with its pulsation mass. Stellar pulsation theory provides a means of determining the masses of pulsating classical Cepheid supergiants—it is the pulsation that causes their luminosity to vary. Such pulsational masses are found to be smaller than the masses derived from stellar evolution theory: this is the Cepheid mass discrepancy problem 1 , 2 , for which a solution is missing 3 , 4 , 5 . An independent, accurate dynamical mass determination for a classical Cepheid variable star (as opposed to type-II Cepheids, low-mass stars with a very different evolutionary history) in a binary system is needed in order to determine which is correct. The accuracy of previous efforts to establish a dynamical Cepheid mass from Galactic single-lined non-eclipsing binaries was typically about 15–30% (refs 6 , 7 ), which is not good enough to resolve the mass discrepancy problem. In spite of many observational efforts 8 , 9 , no firm detection of a classical Cepheid in an eclipsing double-lined binary has hitherto been reported. Here we report the discovery of a classical Cepheid in a well detached, double-lined eclipsing binary in the Large Magellanic Cloud. We determine the mass to a precision of 1% and show that it agrees with its pulsation mass, providing strong evidence that pulsation theory correctly and precisely predicts the masses of classical Cepheids.

The instability strip (IS) of classical Cepheids has been extensively studied theoretically. Comparison of the theoretical IS edges with those obtained empirically, using the most recent Cepheids catalogs available, can provide us with insights into the physical processes that determine the position of the IS boundaries. We investigate the empirical positions of the IS of the classical Cepheids in the Large Magellanic Cloud (LMC) using data of classical fundamental-mode and first-overtone LMC Cepheids from the OGLE-IV variable star catalog, together with a recent high-resolution reddening map from the literature. We studied their position on the Hertzsprung-Russell diagram and determined the IS borders by tracing the edges of the color distribution along the strip. We obtain the blue and red edges of the IS in V- and I-photometric bands, in addition to Teff and log L⊙. The results obtained show a break located at the Cepheids’ period of about 3 days, which was not reported before. This phenomenon is most likely explained by the depopulation of second and third crossing classical Cepheids in the faint part of the IS, since blue loops of evolutionary tracks in this mass range do not extend blueward enough to cross the IS at the LMC metallicity. Furthermore, our empirical borders show good agreement with theoretical ones published in the literature. This proves that our empirical IS is a useful tool to put constraints on theoretical models.

The pulsating star OGLE-BLG-RRLYR-02792 is known to be a member of an eclipsing binary system, and its mass is now determined to be only 0.26 times that of the Sun, meaning that it cannot be a classical RR Lyrae pulsator. A new class of variable star: not RR Lyrae Astronomers use pulsating variable stars of the RR Lyrae type as indicators of the ages of galaxies, and as tools to measure distances to nearby galaxies. So the news that one of these stars had apparently been found as part of an eclipsing binary system was welcome: it meant that the mass of one of these pulsators, previously available only from models, could be unambiguously determined. But the story is not that simple. Pietrzyński et al . have now determined that the star in question, known as RRLYR-02792, has a mass 0.26 times that of the Sun. This means that it is not a classical RR Lyrae star. Instead, it seems to be a pulsator with observational properties temporarily similar to those of classical RR Lyrae stars, but with different stellar parameters and a different evolutionary history as part of a close binary. The authors estimate that 0.2% of samples of RR Lyrae variables may by contaminated by systems similar to this one, so distances previously measured using RR Lyrae stars should not be significantly affected by the presence of these binaries. RR Lyrae pulsating stars have been extensively used as tracers of old stellar populations for the purpose of determining the ages of galaxies, and as tools to measure distances to nearby galaxies 1 , 2 , 3 . There was accordingly considerable interest when the RR Lyrae star OGLE-BLG-RRLYR-02792 (referred to here as RRLYR-02792) was found to be a member of an eclipsing binary system 4 , because the mass of the pulsator (hitherto constrained only by models) could be unambiguously determined. Here we report that RRLYR-02792 has a mass of 0.26 solar masses ( ) and therefore cannot be a classical RR Lyrae star. Using models, we find that its properties are best explained by the evolution of a close binary system that started with and stars orbiting each other with an initial period of 2.9 days. Mass exchange over 5.4 billion years produced the observed system, which is now in a very short-lived phase where the physical properties of the pulsator happen to place it in the same instability strip of the Hertzsprung–Russell diagram as that occupied by RR Lyrae stars. We estimate that only 0.2 per cent of RR Lyrae stars may be contaminated by systems similar to this one, which implies that distances measured with RR Lyrae stars should not be significantly affected by these binary interlopers.

Information support for decision making for planning activities in the Arctic and management of the Arctic territories of the Russian Federation using spatial information visualization tools is an important and urgent task. To effectively address this challenge, it is necessary to develop specialized information tools that focus on the analysis, processing, and visualization of large amounts of information to support decision-making. Such tools include methods and technologies for extracting spatial data from texts in natural language for their further visualization. This paper describes the first part of a large complex of research works aimed at creating methods, technologies, algorithms and software for visualization of spatial data extracted from texts in natural language. At this stage of the work the technology of geodata extraction from the Arctic texts written in Russian is being developed. The paper also substantiates the prospects of application of the created methods and tools to support decision making in the field of territory planning and regional management. The review of named entities recognition problems on the basis of the analysis of scientific works executed in various areas of processing and the analysis of texts is resulted. The main approaches to text analysis and the most significant results achieved so far in this area are considered. The technology developed by the authors to extract spatial data from texts to support decision-making in planning and management of territories is part of a larger system to support socio-economic development of the region. This system is primarily focused on the Arctic territories of the Russian Federation and includes modules for analysis and visualization of geodata identified in the text analysis. The paper describes the research problem, the methods and tools used for text analysis, as well as the main results.

The problem of monitoring and management of industrial and natural complexes in the Arctic is an important problem, without solving which the effective development of the Arctic zones of the Russian Federation is impossible. Specialized information systems are actively used to support decision-making on planning and managing various types of activities in the Arctic, as well as the socio-economic development of the Arctic territories of the Russian Federation. Spatial information visualization tools are an important part of such systems. Visual representation of data is one of the most convenient types of information representation for human processing. This paper describes a method of automated geoimage generation for decision support systems based on the analysis of natural language texts. The use of such geoimages reduces the complexity of decision making for the management tasks of spatially distributed bio-socio-economic systems of the region. The paper describes the formulation of the research problem, review of geocoding tools and services, the original technology of automated geoimages (digital maps) generation based on the use of cloud geoservices. Particular attention is paid to the problem of recognition of named entities in natural language text. The recognition results are used as input data for geocoding and geovisualization process. As a result of the method, the text is converted into a geoimage (map) which can be used to support decision-making by a decision maker. In the final part of the paper, plans for further work are described to develop the capabilities of the automated geoimage generation method for decision support systems based on the analysis of natural language texts.

Purpose To investigate the individual pattern of acute mucosal radiation reactions (AMRR) in patients with head and neck cancer who were treated with radiotherapy alone. Reactions were evaluated daily on an individual basis according to the Dische scoring system. Materials and methods Treatment of 87 head and neck cancer patients comprised either conventional fractionation- (CF; n = 33), accelerated fractionation (AF; n = 33), hyperfractionated- (HPEFX; n = 12) or hypofractionated (HPOFX; n = 9) radiotherapy with radical intent. Daily evaluation of AMRR progression was performed prospectively using a modified, morphologically functional Dische scoring system. The daily sums of the score parameters were subsequently used to construct an individual AMRR course curve for each patient. Results A latency period ranging from 3 to 14 days between the start of radiotherapy and the occurrence of the first AMRR symptom was observed in all patients. Based on the three different shapes of AMRR course curve observed during radiotherapy, three types of AMRR course can be described: (1) a continual increase in AMRR intensity until the completion of radiotherapy; (2) the incidence of a plateau phase following the increase in AMRR (increase–plateau course) and (3) decreasing AMRR intensity with a healing phase. A continual increase in AMRR intensity was observed in about 25 % of CF and AF patients and in more than 50 % of HPOFX treatments. This type of reaction was not observed in the HPEFX group. The increase–plateau course was noted in the majority of AF and CF patients; in almost half of those treated with HPOFX and in all HPEFX patients. A decreasing AMRR intensity course was observed in 23 % of all patients, although not observed at all in the HPEFX and HPOFX fractionation groups. Conclusion The course of AMRR during radiotherapy can differ between individual patients. After the initial increase in AMRR intensity, a stabilization of the reaction—visible as a plateau phase on the course curve—is observed in the majority of patients. A proportion of the irradiated patients experience a continual increase in AMRR intensity up until the end of radiotherapy. A further group of patients exists in whom signs of AMRR healing are observed during the final stages of radiotherapy.

Purpose The goal of this research was to evaluate the healing processes of acute mucosal radiation reactions (AMRR) in patients with head and neck cancer. Materials and methods In 46 patients with oral and oropharyngeal cancer patients irradiated with conventional (n = 25) and accelerated (n = 21) dose fractionation AMRR was evaluated daily during and after radiotherapy. Complex of morphological and functional symptoms according to the Dische score were collected daily until complete healing. Results Duration of healing after the end of radiotherapy ranged widely (12–70 days). It was on the average 8 days longer for accelerated than for conventional radiotherapy (p = 0.016). Duration of dysphagia was also longer for accelerated irradiation (11 days, p   =   0.027). Three types of morphological symptoms were observed as the last symptom at the end of AMRR healing: spotted and confluent mucositis, erythema, and edema. Only a slight correlation between healing duration and area of irradiation fields (r   =   0.23) was noted. In patients with confluent mucositis, two morphological forms of mucosal healing were observed, i.e., marginal and spotted. The spotted form was noted in 71% of patients undergoing conventional radiotherapy and in 38% of patients undergoing accelerated radiotherapy. The symptoms of mucosal healing were observed in 40% patients during radiotherapy. Conclusion The wide range of AMRR healing reflects individual potential of mucosa recovery with longer duration for accelerated radiotherapy. Two morphological forms of confluent mucositis healing were present: marginal and spotted. Healing of AMRR during radiotherapy can be observed in a significant proportion of patients.

We present a precise and accurate measurement of the distance to the Large Magellanic Cloud based on late-type eclipsing-binary systems. Our results provide curently the most accurate zero point for the extragalactic distance scale.