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We estimate the parameters of the donor of the accreting black-hole binary MAXI J1820+070. The measured values of the binary period, rotational and radial velocities and constraints on the orbital inclination imply the donor is a subgiant with the mass of $M_2\approx 0.49^{+0.10}_{-0.10}M_\odot$ and the radius of $R_2\approx 1.19^{+0.08}_{-0.08}R_\odot$. We re-analyze the previously obtained optical spectrum from the Gran Telescopio Canarias, and found it yields a strict lower limit on the effective temperature of $T>4200$ K. We compile optical and infrared fluxes observed during the quiescence of this system. From the minima $r$ and $i$-band fluxes found in Pan-STARSS1 Data Release 2 pre-discovery imaging and for a distance of $D\approx3$ kpc, reddening of $E(B$--$V)=0.23$ and $R_2\approx{1.11R_\odot}$, we find $T\lesssim4230$ K, very close to the above lower limit. For a larger distance, the temperature can be higher, up to about 4500 K (corresponding to a K5 spectral type, preferred by previous studies) at $D=3.5$ kpc, allowed by the Gaia parallax. We perform evolutionary calculations for the binary system and compare them to the observational constraints. Our model fitting the above temperature and radius constraints at $D\approx 3$ kpc has the mass of $0.4M_\odot$, $T\approx4200$ K and solar metallicity. Two alternative models require $D\gtrsim 3.3$--3.4 kpc at $0.4 M_\odot$, $T\approx4500$ K and half solar metallicity, and $0.5M_\odot$, $T\approx4300$ K and solar metallicity. These models yield mass transfer rates of $\sim\!\!10^{-10}M_\odot$/yr, compatible with those based on the estimated accreted mass of $\approx\!2\times 10^{25}$ g and the time between the 2018 discovery and the 1934 historical outburst., ApJ, in press

We analyse properties of the mass outflow from the Roche-lobe filling component of a semi-detached binary system. We follow the approaches published by Paczy��ski \& Sienkiewicz and by Lubow \& Shu, which we compare with other simplified approaches. We find that the density of the flow at $L_1$ is orders of magnitude lower than the density on the same equipotential but away from $L_1$. Furthermore, the effective cross section of the flow, after averaging over its profile of the momentum density, is much lower than some published estimates done without accounting for the averaging. Thus, the use of some simplified formulae for the density and the flow cross section can lead to overestimates of the accretion rate and of the mass contained in the $L_1$ regions by very large factors unless they are supported by simultaneous integrations of the equations of stellar structure for the outer layers of the donor., MNRAS, in press

The evolution of massive stars is influenced by the mass lost to stellar winds over their lifetimes. These winds limit the masses of the stellar remnants (such as black holes) that the stars ultimately produce. We use radio astrometry to refine the distance to the black hole X-ray binary Cygnus X-1, which we find to be $2.22^{+0.18}_{-0.17}$ kiloparsecs. When combined with previous optical data, this implies a black hole mass of $21.2\pm2.2$ solar masses, higher than previous measurements. The formation of such a high-mass black hole in a high-metallicity system constrains wind mass loss from massive stars., Published online in Science on 2021 February 18; Main (3 figures; 1 Table) + Supplementary (11 figures; 3 Tables)

We present a comprehensive description of the Sch\"onberg--Chandrasekhar (S--C) transition, which is an acceleration of the stellar evolution from the nuclear to the thermal time scales occurring when the fractional mass of the helium core reaches a critical value, about 0.1. It occurs in the 1.4 to 7 M$_\odot$ mass range due to impossibility of maintaining the thermal equilibrium after the nuclear energy sources in the core disappear. We present the distributions of the hydrogen abundance, the energy generation rate and the temperature for stars crossing that limit. We confirm that a sharp S--C limit is present for strictly isothermal cores, but it is much smoother for real stars. The way the boundary of the core is defined is important for the picture of this transition. With a strict definition of the core as the region where the helium abundance is close to null, it occurs in an extended range of the fractional core mass of roughly 0.03 to 0.11. The cause of that is a gradual core contraction causing a correspondingly gradual loss of the core isothermality with the increasing core mass. On the other hand, when using definitions allowing for some H abundance in the core, the S--C transition is found to be sharper, at the fractional core mass of between about 0.07 and 0.11. Still, it is more a smooth transition than a sharp limit. We have also searched for specific signatures of that transition, and found that it is associated with the stellar radius first decreasing and then increasing again. We have considered whether the S--C limit can be used as a diagnostic constraining the evolutionary status of accreting X-ray binaries, but found such uses unfounded., Comment: MNRAS, in press, 6 pages

We consider constraints on the distance, inclination and component masses in the X-ray binary GX 339--4 resulting from published works, and then construct detailed evolutionary models for the donor. From both considerations, and assuming the black-hole nature for the compact object (i.e., its mass $>3\rm{M}_{\odot}$), the possible donor mass is $\approx$0.5--$1.4\rm{M}_{\odot}$, the inclination is $\approx{40}^\circ$--$60^\circ$ and the distance is $\approx$8--12\,kpc. The corresponding mass of the compact object is $\approx$4--$11\rm{M}_{\odot}$. We then confirm a previous estimate that the theoretical conservative mass transfer rate in GX 339--4 is $\lesssim{10^{-9}}\rm{M}_{\odot}$ yr$^{-1}$. This is $\gtrsim$10 times lower than the average mass accretion rate estimated from the long-term X-ray light curve. We show that this discrepancy can be solved in two ways. One solution invokes irradiation of the donor by X-rays from accretion, which can temporarily enhance the mass transfer rate. We found that absorption of a $\sim$1 per cent of the irradiating luminosity results in the transfer rate equal to the accretion rate. The time scale at which the transfer rate will vary is estimated to be $\sim$10 yr, which appears consistent with the observations. The other solution invokes non-conservative mass transfer. This requires that $\approx$70 per cent of the transferred mass escapes as a strong outflow and carries away the specific angular momentum comparable to that of the donor., MNRAS, 9 pages, in press

We consider donor evolution and mass transfer in the microquasar V404 Cyg/GS 2023+338. Based on X-ray observations of its two outbursts, its average mass accretion rate is substantially lower than our model mass-loss rate from its low-mass giant donor. A likely solution to this discrepancy is that a large fraction of the mass flowing from the donor leaves the binary in the form of outflows from the accretion disc around the accretor. The outflow can be parameterizes by the fractions of the mass and angular momentum leaving the system. We calculate the latter as a function of the radius of the accretion disc from which the outflow takes place. We then perform detailed evolutionary calculations for V404 Cyg. Given our estimated average accretion rate, $>$70 per cent of the mass lost from the donor has to leave the binary. The allowed solutions for the actual donor mass loss rate are parameterized by our two outflow parameters. Our results are in agreement with the observed outflows from the outer disc as well as with the variable near-Eddington accretion observed during the outbursts, compatible with outflows from the vicinity of the black hole. We then calculate the expected rate of the orbital period change. Its future measurements can constrain the presence of an outflow in V404 Cyg and its parameters., MNRAS, in press, 7 pages

The donor in the microquasar GRS 1915+105 is a low-mass giant. Such a star consists of a degenerate helium core and a hydrogen-rich envelope. Both components are separated by a hydrogen burning shell. The structure of such an object is relatively simple and easy to model. Making use of the observational constraints on the luminosity and the radius of the donor, we constrain the mass of this star with evolutionary models. We find a very good agreement between the constraints from those models and from the observed rotational broadening and the NIR magnitude. Combining the constraints, we find solutions with stripped giants of the mass of $\geq\!0.28{\rm M}_{\odot}$ and of the spectral class K5 III, independent of the distance to the system, and a distance-dependent upper limit, $\lesssim\!1{\rm M}_{\odot}$. We also calculate the average mass transfer rate and the duty cycle of the system as a function of the donor mass. This rate is much below the critical rate (at which the system would become persistent), and the duty cycle is less than 20 per cent., Comment: MNRAS, in press

We constrain the binary parameters of the eclipsing accreting X-ray binary IGR J17451--3022 and the nature of its donor star. The donor mass, its radius, and the system inclination angle are computed based on the system orbital period and eclipse duration recently reported by Bozzo et al.\ (2016). We find that the donor is most likely a main-sequence star with the mass comprised within the range $\sim$(0.5--$0.8){\rm M}_{\odot}$ and the radius of $\sim\! 0.7{\rm R}_{\odot}$. Assuming that the accreting compact object in IGR J17451--3022 is a neutron star, the duration of the nearly total rectangular eclipses yields the inclination angle of the system of $71^\circ\lesssim i\lesssim 76^\circ$, compatible with the presence of dips in this system. We rule out the presence of either brown or white dwarf. However, we find an alternative possibility that the donor star in IGR J17451--3022 could be a partially stripped giant with a very low mass, $\sim\! 0.2{\rm M}_{\odot}$. This case requires a substantial mass loss prior to the formation of the giant-star He core. According to that solution, the radius would be $\sim\! 0.4{\rm R}_{\odot}$, at $i\sim 80^\circ$. We additionally show that the well-known approximate dependence of the giant-star radius exclusively on its core mass breaks down below $\sim\!0.3{\rm M}_{\odot}$., Comment: Astronomy & Astrophysics, in press

Endotracheal suction is essential to keep the respiratory capacity of the bronchial tree. The aim of this study was to establish the principles reducing potential side-effects, like hypoxia, bradycardia, hypotension, arrhythmia, nosocomial infections. Analysing the literature we have selected the following major beneficial factors: 1:2 to 2:3 cathether - tracheal tube diameter ratio, individual adjustment of the suctioning frequency, maximal duration of the procedure capped at 10-15 sec., minimal effective suctioning pressure of 80-100 mmHg. We have also determined that the following procedures should be also taken into consideration: preoxygenation (only for unstable patients), sedation and analgesia. We have concluded with the comparison of the two suction systems, pointing out that, especially for unstable patients, closed-suction system proves more suitable.

Our calculations of stellar population synthesis indicate that the Galaxy contains (depending on the assumptions) some 1000 to 40,000 X‐ray binaries with a black hole (BH) component. For the most likely set of assumptions, this number is equal to about 15,000. Most of these objects are transient systems (dormant for most of the time). The distribution of the orbital periods of the expected population agrees reasonably well with the observed one based on the sample of ∼30 known galactic BH X‐ray binaries with determined periods. The expected distribution of the BH masses does not agree and our calculations predict too many low mass (2–3 M⊙) BHs.

At present, 117 Be/neutron star (Be/NS) X‐ray binaries (XRBs) are known in the Galaxy and the Magellanic Clouds, but not a single Be/black hole (Be/BH) binary has been found so far. We carried out the calculations of stellar population synthesis to investigate the case of the apparently missing population of Be/BH XRBs. According to our calculations, the main reason of this disparity is the fact that within the orbital period range where Be XRBs are found, these systems are formed predominantly with a NS componnent. The systems with a BH component are formed predominantly with much longer orbital periods and they are not easy to detect.

Values of black hole masses are frequently determined with the help of the reverberation method. This method is based on the measurements of widths of the broad emission lines as well as time delays between the lines and the continuum. The above method requires a specific assumption about the distribution of the orbits of the Broad Line Region (BLR) clouds. In the case of a spherical cloud distribution, the geometrical factor f2 = 0.75 [1] which corresponds to this geometry is adopted. [2] determined the value f2 ∼ 1.37 The determined value is based on the relation of the black hole mass to the velocity dispersion. In our calculations we have determined this factor by using an independent mass determination from the X‐ray variance method (based on X‐ray variability) for a number of Seyfert 1 galaxies. The value of f2 is equal to 1.12 ± 0.54. Both values are larger than 0.75 and show that the BLR is rather more flat than spherical.

Present status of the possible black hole microlensing events and the present understanding of high frequency quasi-periodic oscillations in systems containing black hole candidates (BHCs) are briefly discussed. The growing evidence for the presence of the event horizons around some compact objects is reviewed. Finally, the news from four individual objects (SS 433, GX 339-4, CI Cam and Cyg X-3) are presented and the updated list of BHCs, containing 49 objects is given., 15 pages; 2 figures; presented at Vulcano Workshop 2003; accepted for publication in Chinese Journal of Astronomy and Astrophysics

The aim of this paper is to argue that some day in the not-too-distant future one of the well-known X-ray pulsars, say, Cen X-3 (although better examples would be probably GX 301-2 or GX 1+4), will disappear from the X-ray sky. It will reappear again after some, say, tens of years and its pulse period will be then longer than it is now.

Three situations involving mass loss from binary systems are discussed. (1) Non-conservative mass exchange in semi-detached binaries. No quantitative estimate of this mechanism is possible at present. (2) Common envelope binaries. There are both theoretical and observational indications that this phase of evolution happens to many systems, even to some that are not very close initially (orbital periods ~ years). (3) Stellar winds in binaries. Observational evidence suggests that stellar winds from components of close binaries (especially semi-detached) are significantly stronger than from single stars at the same location in the H-R diagram. Theoretical arguments indicate that in some cases stellar wind may stabilize the component of a binary against the Roche lobe overflow. In some cases there is weak evidence of an anisotropy in the stellar wind.

The central concept of anthropology as a humanistic discipline is that of culture. The use of "culture", although operative since the Ancient era, derives mainly from social evolutionism and Kuiturgeschichte of the XIX century. The turning point in the development of cultural (social) anthropology was the work of an Englishman, E. B. lyior. Since his "Primitive Culture" (London 1871) it became possible to speak of culture in general and of particular cultures. It is difficult to settle upon a single definition of this complex term. A.L. Kroeber and C. Kluckhohn analysed 168 definitions of culture. These appeared, as judged by general emphasis, to fall into six major groups: 1) enumeratively descriptive, 2) historical, 3) normative, 4) psychological, 5) structural, 6) genetic. The term "cultural anthropology" is more widely used in the United States whereas in Britain the term "social anthropology" is predominant. In Central Europe, particularly in German-speaking countries, the term "anthropology" has been reserved for biological aspects of man’s life. The study of cultural dimension of man’s existence appears under the label of ethnology (the theoretical and generalizing aspect) and ethnography (the descriptive aspect). This pattern has been followed, by and large, by Polish scientific community. However, there is too much overlap to warrant keeping apart "cultural" from "social" anthropology. The subject matter of the discipline is essentially two-dimensional, being always both "cultural" and "social". All human behaviour is influnced by cultural standards, and conversely culture itself is essentially social, in its transmission and distribution among the members of a society. Many anthropologists therefore either speak of social and cultural anthropology jointly or fuse them into a single term "sociocultural anthropology". In the growth of the discipline, one can discern several theoretical orientations. 1) Evolutionism - the application of the general theory of evolution to cultural phenomena as distinguished from biological or physical phenomena. Cultural evolution is conceived as a continuous and usually accumulative process, by which cultural phenomena undergo change, one form or stage succeeding another. 2) Diffusion ism - a term to refer to all the orderly processes which produce cultural similarities in various societies other than invention. The concept of the Kulturkreis, coined by the German culture-historical school, has proved to be most influential and representative for this school of thought. 3) Historicism - the emphasis on historically created diversities, leaving to psychology the exploration of common human nature. Every aspect of culture must be considered in the total context in which it occurred. F. Boas was a leading exponent of this way of viewing anthropology. 4) Culture and personality approach - the stress laid upon the interaction between culture and personality formation. Culture exists only in human personalities; motives, emotions and values are institutionalized in culture. 5) Functionalism - the explanation of anthropological facts by the part which they play within the integral system of culture and by the manner in which they are related to each other. Functionalism, propounded by B. Malinowski and A. R. Radcliffe-Brown, became the theoretical foundation of the British social anthropology with its emphasis on organization and social structure. 6) Structuralism - a thesis of fundamental constancy of structural, unconscious equipment of man (its main representative is C. Lévi-Strauss). In order to reach the structure of socio-cultural reality, a process of symbolization (converting facts into signs) is required. 7) Ncocvoluliotiism - an attempt to revive, refine and test the theory of cultural evolution, particularly with regard to its unilinear or multilinear character. Within this orientation the interdisciplinary discussion is being held on the interaction between biology and culture. Human evolution is considered the history of feedback relationship between organism and behaviour. Human behaviour can best be described as biocultural behaviour. Man is viewed more and more in a holistic way. The emergence of anthropology tout court, an integrated science of man, is a logical consequence of this stance.

The target ofthe FPSO structural design is firstly to guarantee structural integrity. At the same time it needs to target in minimizing the limitations on the oil and gas production related functions caused by the structural design. The structural design concept developed for this aim is discussed with emphasis on the practical management aspects. The FPSO steel model is developed within a 3D product model supporting all the other disciplines as well. The structural analyses utilize the steel model as a basis for FEA model development. For the structural design analyses a broad spectrum of programs is available ranging from initial design tools to the high end state-of-the-art analysis software. Spectral based procedures are frequently utilized. The load, strength and fatigue analysis capabilities of the design system are illustrated with case examples. The work of the designers is supported by a management framework and procedures adapted for structural design discipline and the use of state-of-the-art analysis software.