scholarly journals Modeling of the Wind/Disk Outflow from Be Stars

Universe ◽  
2021 ◽  
Vol 7 (10) ◽  
pp. 353
Author(s):  
Sergey Bogovalov ◽  
Maxim Petrov
Keyword(s):  
Numerical Modeling ◽  
Turbulent Viscosity ◽  
Be Stars ◽  
Rotating Stars ◽  
Polar Wind ◽  
Hydrodynamic Turbulence ◽  
Plasma Ions ◽  
High Level ◽  
First Time ◽  
Fast Rotating

The objective of this work is to reproduce the formation of the fast polar wind and viscous disk outflow from Be stars in a unified physical picture. Numerical modeling of the plasma outflow from fast rotating stars was performed taking into account the acceleration of the plasma due to scattering of the radiation of the star in lines of plasma ions and excitation of the hydrodynamic turbulence in the outflow. The fast polar wind naturally arises in this picture with an expected flow rate. For the first time, it is shown that a disk-like outflow with a relatively high level of turbulence is formed at the equator of fast rotating stars emitting radiation-driven wind. However, the level of turbulent viscosity is well below the level necessary for the formation of a Keplerian disk.

Modeling of stellar wind from fast rotating stars

2018 ◽  
Vol 27 (10) ◽  
pp. 1844004 ◽  
Author(s):  
S. V. Bogovalov ◽  
S. M. Romanikhin
Keyword(s):  
Stellar Wind ◽  
Large Scale ◽  
Reynolds Numbers ◽  
Nonuniform Distribution ◽  
Polar Regions ◽  
Rotating Stars ◽  
Efficient Diffusion ◽  
Rotating Star ◽  
High Level ◽  
Fast Rotating

Two-dimensional (2D) axisymmetric hydrodynamic model for the stellar wind outflow from a fast rotating star is created. Nonuniform distribution of the pressure over the surface of the star corresponding to the condition of equilibrium in every point of plasma in the gravitational and centrifugal fields is taken into account. We also take into account the turbulence of the flow excited in the wind at Reynolds numbers [Formula: see text]. Calculations show the formation of the disklike outflow from the surface of the star at the equator which rather quickly (on the scale of the order of the radius of the star) expands into polar regions. Huge vertex is formed at high latitudes where high level of turbulence makes possible efficient diffusion of the angular moment. At the same time the turbulence is not excited at the equator. This prevents formation of the large scale disklike outflow at the equatorial plane. Dependence of the mass flux outflow on the velocity of the star rotation is obtained.

scholarly journals Chemical abundances of fast-rotating OB stars

2014 ◽  
Vol 9 (S307) ◽  
pp. 94-95
Author(s):  
Constantin Cazorla ◽  
Thierry Morel ◽  
Yaël Nazé ◽  
Gregor Rauw
Keyword(s):  
Massive Stars ◽  
Evolutionary Models ◽  
Rotating Stars ◽  
Chemical Abundances ◽  
Single Star ◽  
Ob Stars ◽  
Detailed Surface ◽  
Normal Nitrogen ◽  
First Time ◽  
Fast Rotating

AbstractFast rotation in massive stars is predicted to induce mixing in their interior, but a population of fast-rotating stars with normal nitrogen abundances at their surface has recently been revealed (Hunter et al.2009; Brott et al.2011, but see Maeder et al.2014). However, as the binary fraction of these stars is unknown, no definitive statements about the ability of single-star evolutionary models including rotation to reproduce these observations can be made. Our work combines for the first time a detailed surface abundance analysis with a radial-velocity monitoring for a sample of bright, fast-rotating Galactic OB stars to put strong constraints on stellar evolutionary and interior models.

scholarly journals Equatorial mass loss from Be stars

2010 ◽  
Vol 6 (S272) ◽  
pp. 640-641
Author(s):  
Cyril Georgy ◽  
Sylvia Ekström ◽  
Anahí Granada ◽  
Georges Meynet
Keyword(s):  
Mass Loss ◽  
Be Stars ◽  
Rotating Stars ◽  
Single Star ◽  
Star Models ◽  
Total Mass Loss ◽  
Rotation Phase ◽  
Rotating Star ◽  
Mechanical Mass ◽  
Fast Rotating

AbstractBe stars are thought to be fast rotating stars surrounded by an equatorial disc. The formation, structure and evolution of the disc are still not well understood. In the frame of single star models, it is expected that the surface of an initially fast rotating star can reach its keplerian velocity (critical velocity). The Geneva stellar evolution code has been recently improved, in order to obtain some estimates of the total mass loss and of the mechanical mass loss rates in the equatorial disc during the whole critical rotation phase. We present here the first results of the computation of a grid of fast rotating B stars evolving towards the Be phase, and discuss the first estimates we obtained.

scholarly journals Two-dimensional models of early-type fast rotating stars: the ESTER project

2015 ◽  
Vol 11 (A29B) ◽  
pp. 147-148
Author(s):  
Michel Rieutord
Keyword(s):  
Main Sequence ◽  
Mass Star ◽  
Two Dimensional ◽  
Be Stars ◽  
Rotating Stars ◽  
Intermediate Mass ◽  
Fundamental Parameters ◽  
Intermediate Mass Stars ◽  
Intermediate Mass Star ◽  
Fast Rotating

AbstractIn this talk I present the latest results of the ESTER project that has taken up the challenge of building two dimensional (axisymmetric) models of stars rotating at any rotation rate. In particular, I focus on main sequence massive and intermediate mass stars. I show what should be expected in such stars as far as the differential rotation and the associated meridional circulation are concerned, notably the emergence of a Stewartson layer along the tangent cylinder of the core. I also indicate what may be inferred about the evolution of an intermediate-mass star at constant angular momentum and how Be stars may form. I finally give some comparisons between models and observations of the gravity darkening on some nearby fast rotators as it has been derived from interferometric observations. In passing, I also discuss how 2D models can help to recover the fundamental parameters of a star.

A Confrontation between Two Doctrines: The Birth of Struggle for Hegemony in Hebrew Children's Literature during the 1930s and 1940s

2008 ◽  
Vol 1 (2) ◽  
pp. 139-155 ◽  
Author(s):  
YAEL DARR
Keyword(s):  
Children's Literature ◽  
Educational System ◽  
Single Channel ◽  
Children’S Literature ◽  
The Political ◽  
Literary Creation ◽  
History Of ◽  
High Level ◽  
First Time ◽  
Literary Quality

This article describes a crucial and fundamental stage in the transformation of Hebrew children's literature, during the late 1930s and 1940s, from a single channel of expression to a multi-layered polyphony of models and voices. It claims that for the first time in the history of Hebrew children's literature there took place a doctrinal confrontation between two groups of taste-makers. The article outlines the pedagogical and ideological designs of traditionalist Zionist educators, and suggests how these were challenged by a group of prominent writers of adult poetry, members of the Modernist movement. These writers, it is argued, advocated autonomous literary creation, and insisted on a high level of literary quality. Their intervention not only dramatically changed the repertoire of Hebrew children's literature, but also the rules of literary discourse. The article suggests that, through the Modernists’ polemical efforts, Hebrew children's literature was able to free itself from its position as an apparatus controlled by the political-educational system and to become a dynamic and multi-layered field.

scholarly journals Aberrant Expression of TLR2, TLR7, TLR9, Splicing Variants of TLR4 and MYD88 in Chronic Lymphocytic Leukemia Patients

2021 ◽  
Vol 10 (4) ◽  
pp. 867
Author(s):  
Katarzyna Skorka ◽  
Paulina Wlasiuk ◽  
Agnieszka Karczmarczyk ◽  
Krzysztof Giannopoulos
Keyword(s):  
Bone Marrow ◽  
Chronic Lymphocytic Leukemia ◽  
Cytotoxic T Cells ◽  
Lymphocytic Leukemia ◽  
Aberrant Expression ◽  
Downstream Signaling ◽  
Splicing Variants ◽  
High Level ◽  
Time To First Treatment ◽  
First Time

Functional toll-like receptors (TLRs) could modulate anti-tumor effects by activating inflammatory cytokines and the cytotoxic T-cells response. However, excessive TLR expression could promote tumor progression, since TLR-induced inflammation might stimulate cancer cells expansion into the microenvironment. Myd88 is involved in activation NF-κB through TLRs downstream signaling, hence in the current study we provided, for the first time, a complex characterization of expression of TLR2, TLR4, TLR7, TLR9, and MYD88 as well as their splicing forms in two distinct compartments of the microenvironment of chronic lymphocytic leukemia (CLL): peripheral blood and bone marrow. We found correlations between MYD88 and TLRs expressions in both compartments, indicating their relevant cooperation in CLL. The MYD88 expression was higher in CLL patients compared to healthy volunteers (HVs) (0.1780 vs. 0.128, p < 0.0001). The TLRs expression was aberrant in CLL compared to HVs. Analysis of survival curves revealed a shorter time to first treatment in the group of patients with low level of TLR4(3) expression compared to high level of TLR4(3) expression in bone marrow (13 months vs. 48 months, p = 0.0207). We suggest that TLRs expression is differentially regulated in CLL but is similarly shared between two distinct compartments of the microenvironment.

scholarly journals Revealing the constituents of Egypt’s oldest beer using infrared and mass spectrometry

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Mohamed A. Farag ◽  
Moamen M. Elmassry ◽  
Masahiro Baba ◽  
Renée Friedman
Keyword(s):  
Large Scale ◽  
Beer Brewing ◽  
Chemical Signatures ◽  
Chemical Determination ◽  
Materials Used ◽  
High Level ◽  
Beer Production ◽  
First Time ◽  
Detailed Chemical

Abstract Previous studies have shown that the Ancient Egyptians used malted wheat and barley as the main ingredients in beer brewing, but the chemical determination of the exact recipe is still lacking. To investigate the constituents of ancient beer, we conducted a detailed IR and GC-MS based metabolite analyses targeting volatile and non-volatile metabolites on the residues recovered from the interior of vats in what is currently the world’s oldest (c. 3600 BCE) installation for large-scale beer production located at the major pre-pharaonic political center at Hierakonpolis, Egypt. In addition to distinguishing the chemical signatures of various flavoring agents, such as dates, a significant result of our analysis is the finding, for the first time, of phosphoric acid in high level probably used as a preservative much like in modern beverages. This suggests that the early brewers had acquired the knowledge needed to efficiently produce and preserve large quantities of beer. This study provides the most detailed chemical profile of an ancient beer using modern spectrometric techniques and providing evidence for the likely starting materials used in beer brewing.

Cyclic Methylsiloxanes as Working Fluids for Space Power Cycles

1993 ◽  
Vol 115 (3) ◽  
pp. 130-137 ◽  
Author(s):  
G. Angelino ◽  
C. Invernizzi
Keyword(s):  
High Temperature ◽  
Full Potential ◽  
Working Fluids ◽  
Power Cycles ◽  
Thermodynamic Performance ◽  
High Level ◽  
Organic Fluids ◽  
Large Wheel ◽  
Turbine Exhaust ◽  
Fast Rotating

The potential merits of cyclic polymethylsiloxanes, particularly those conventionally denominated D4 and D5, as working fluids for space power cycles are discussed. The attractive technical characteristics of these substances which are fully nontoxic, moderately flammable, and stable at high temperature are presented. Some experimental results on vapor pressure and on thermal stability are reported. A maximum operating temperature of about 400°C appears achievable. A comprehensive thermodynamic analysis comparing siloxanes with other classes of high temperature fluids is performed. The peculiar characters of siloxane cycles are found to be: a good overall efficiency achieved through a massive regeneration, a moderate expansion work, and an abundant volume flow at turbine exhaust. A number of two-stage turbines for two power levels (i.e., 30 and 5 kW) were designed using an appropriate optimization program. The resulting main features of such expanders were a satisfactory efficiency, a low rotating and peripheral speed, and a comparatively large wheel diameter. These characteristics seem of particular interest for low capacity systems where, with other fluids, turbines tend to be impractically small and fast rotating and where a high level of regeneration becomes more acceptable. In considering for the sake of comparison the thermodynamic performance of many classes of organic fluids, it becomes apparent that the full potential of organic power cycles in view of the variety of future needs has not yet been thoroughly investigated.

PREVENTION ISSUES OF OCCUPATIONAL AND PRODUCTION-RELATED DISEASES IN MINING INDUSTRY WORKERS

2021 ◽  
Author(s):  
G.S. Agzamova ◽  
◽  
N.U. Ibragimova ◽  
Yu.A. Abdieva ◽  
Keyword(s):  
Health Care ◽  
Metallurgical Plant ◽  
Occupational Diseases ◽  
Mining Industry ◽  
Production Environment ◽  
Cardiovascular Pathology ◽  
Dynamic Observation ◽  
High Level ◽  
Medical Examinations ◽  
First Time

Abstract: Protecting and promoting the health of workers in the mining industry is one of the most important problems of occupational pathology and health care. The structure and levels of prevention of occupational diseases are directly dependent on harmful and adverse factors of the production environment and labor process, adequately reflecting the state of production. Purpose: to study the issues of prevention of occupational and production-related diseases of mining and metallurgical plant workers. Research materials and methods: a dynamic observation of the health status of workers in the main industries of the mining and metallurgical plant (800 workers) was carried out. 92 patients with silicosis were examined. Results: Up to 92.8% of first-time occupational diseases are detected during periodic medical examinations. The prevailing sociomatic pathology is cardiovascular pathology, namely, arterial hypertension and diseases of the musculoskeletal system, mainly osteochondrosis of the spine. Prevalence of silicosis was observed in individuals with little professional experience (from 5 years old), young age and primary detection of patients in stage II silicosis, which was accompanied by respiratory failure. Conclusions: The prevention programme developed will ensure a high level of health care in terms of early diagnosis, rehabilitation and secondary prevention of both occupational and occupational diseases.

Innovation in Slovenian tourism organisations

2015 ◽  
Vol 21 (1) ◽  
pp. 51-62
Author(s):  
Maja Uran Maravić ◽  
Dejan Križaj ◽  
Miha Lesjak
Keyword(s):  
Design Methodology ◽  
Mean Value ◽  
Sample Survey ◽  
Research Activity ◽  
Main Hypothesis ◽  
Innovation Activities ◽  
Innovation Climate ◽  
High Level ◽  
Innovation Practices ◽  
First Time

The purpose – Slovenian tourism organisations must constantly focus on developing variety innovations for organisations. In this paper, we present a study conducted on innovation practices in Slovenian tourism organisations. Design/methodology – In a survey conducted on Slovenia tourism organisations, we obtained data and identified their innovation performance and the innovation climate in their area of business. There are three main hypothesis tested. Findings – The research sample of 41 organisations found that most innovation in tourism organisations came through the introduction of new services (90%), followed by innovation through new organisational methods (73%), and found a high-level climate for innovation. Worse was its assessment of research activity within organisations and cooperation with external institutions (eg. universities and research institutes) and investment in innovation activities within their research and development. Results obtained from the research showed a mean value for the innovation climate-instrument of 3.83 indicating a high innovation climate for the Slovenian tourism companies included in the sample survey. Mostly, (publicly known as) more innovative active organisations responded to our survey. From such results, we find that tourism organisations included in the survey are aware of the importance of innovation, teaching organisations to communicate well and network with other organisations, are adaptable to change and engaged with their own ideas in support of the organisation's management. Originality of the research – The contribution of the research is that it has applied the generic instrument for measuring innovation climate on tourism and the first time climate is measured in Slovenia.

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