scholarly journals The Statistical Equilibrium of H and He and the H/He Ratio in WR Stars

1984 ◽  
Vol 86 ◽  
pp. 88-91
Author(s):  
A.B. Underhill ◽  
A.K. Bhatia
Keyword(s):  
Electron Temperature ◽  
Statistical Equilibrium ◽  
Emission Lines ◽  
General Distribution ◽  
Strong Emission ◽  
B Stars ◽  
Effective Temperatures ◽  
The Masses ◽  
Selection Of ◽  
Made In

The mixed selection of strong emission lines present in the spectra of WR stars suggests that we are observing plasma with an electron temperature of the order of 105 K somewhere in the atmospheres of these rare stars. In the spectra of some WR stars emission lines of H are detected; this suggests that plasma with an electron temperature of the order of 104 K may be present also. Since the observations made in the last 30 years show that the masses, luminosities, effective temperatures, and general distribution in space of WR stars are similar to those of stars with spectral types in the range from about B2 to O9, a prime question is why are the spectra of WR stars so different from those of the B stars with which they are associated.

scholarly journals The SAMI Galaxy Survey: reconciling strong emission line metallicity diagnostics using metallicity gradients

2021 ◽  
Vol 502 (3) ◽  
pp. 3357-3373
Author(s):  
Henry Poetrodjojo ◽  
Brent Groves ◽  
Lisa J Kewley ◽  
Sarah M Sweet ◽  
Sebastian F Sanchez ◽  
...  
Keyword(s):  
Emission Line ◽  
Electron Temperature ◽  
Gas Phase ◽  
Mass Range ◽  
Accurate Method ◽  
Emission Lines ◽  
Mass Relation ◽  
Strong Emission ◽  
Data Release ◽  
Accurate Comparison

ABSTRACT We measure the gas-phase metallicity gradients of 248 galaxies selected from Data Release 2 of the SAMI Galaxy Survey. We demonstrate that there are large systematic discrepancies between the metallicity gradients derived using common strong emission line metallicity diagnostics. We determine which pairs of diagnostics have Spearman’s rank coefficients greater than 0.6 and provide linear conversions to allow the accurate comparison of metallicity gradients derived using different strong emission line diagnostics. For galaxies within the mass range 8.5 < log (M/M⊙) < 11.0, we find discrepancies of up to 0.11 dex/Re between seven popular diagnostics in the metallicity gradient–mass relation. We find a suggestion of a break in the metallicity gradient–mass relation, where the slope shifts from negative to positive, occurs between 9.5 < log (M/M⊙) < 10.5 for the seven chosen diagnostics. Applying our conversions to the metallicity gradient–mass relation, we reduce the maximum dispersion from 0.11 dex/Re to 0.02 dex/Re. These conversions provide the most accurate method of converting metallicity gradients when key emission lines are unavailable. We find that diagnostics that share common sets of emission line ratios agree best, and that diagnostics calibrated through the electron temperature provide more consistent results compared to those calibrated through photoionization models.

scholarly journals Non-local thermodynamic equilibrium line formation for Si i–ii–iii in A–B stars and the origin of Si ii emission lines in ι Her

2020 ◽  
Vol 493 (4) ◽  
pp. 6095-6108 ◽  
Author(s):  
Lyudmila Mashonkina
Keyword(s):  
Thermodynamic Equilibrium ◽  
Local Thermodynamic Equilibrium ◽  
Emission Lines ◽  
Atomic Data ◽  
Line Formation ◽  
Atmospheric Parameters ◽  
B Stars ◽  
Non Local ◽  
Effective Temperatures ◽  
Model Atom

ABSTRACT A comprehensive model atom was developed for Si i–ii–iii using the most up-to-date atomic data available so far. Based on non-local thermodynamic equilibrium (NLTE) line formation for Si i, Si ii and Si iii and high-resolution observed spectra, we determined the NLTE abundances for a sample of nine unevolved A9–B3 type stars with well-determined atmospheric parameters. For each star, NLTE reduces the line-to-line scatter for Si ii substantially compared with the LTE case and leads to consistent mean abundances from lines of different ionization stages. In the hottest star of our sample, ι Her, Si ii is subject to overionization that drives emission in the lines arising from the high-excitation doublet levels. Our NLTE calculations reproduced 10 emission lines of Si ii observed in ι Her. The same overionization effect leads to greatly weakened Si ii lines, which are observed in absorption in ι Her. Large positive NLTE abundance corrections (up to 0.98 dex for 5055 Å) were useful for achieving consistent mean abundances from lines of the two ionization stages, Si ii and Si iii. It was found that NLTE effects are overestimated for the Si ii 6347, 6371 Å doublet in ι Her, while the new model atom works well for cooler stars. At this stage, we failed to understand this problem. We computed a grid of the NLTE abundance corrections for lines of Si i, Si ii and Si iii in model atmospheres with effective temperatures and surface gravities characteristic of unevolved A–B type stars.

WINTER WHEAT DEVELOPED BY THE UDMURT RESEARCH INSTITUTE OF AGRICULTURE IN COMPETITIVE VARIETY TESTING

2020 ◽  
pp. 5-16
Author(s):  
I.V. TORBINA ◽  
◽  
I.R. FARDEYEVA ◽  
Keyword(s):  
Winter Wheat ◽  
Crop Rotation ◽  
Biological Characteristics ◽  
Commercial Use ◽  
Breeding Material ◽  
Rotation Pattern ◽  
Selection Of ◽  
Variety Testing ◽  
Made In ◽  
Research Institute

The paper assesses the promising varieties of winter wheat in a competitive variety test by the main economic and biological characteristics that determine the suitability of the variety for commercial use. The object of research was the authors’ own breeding material. The experiments on the selection of winter wheat were made in the experimental crop rotation pattern of the Institute.

Evidence-based Assessment

2010 ◽  
pp. 76-98
Author(s):  
John Hunsley ◽  
Eric J. Mash
Keyword(s):  
Decision Making ◽  
Clinical Assessment ◽  
Assessment Process ◽  
Evidence Based ◽  
The Past ◽  
Specific Assessment ◽  
The Many ◽  
Selection Of ◽  
Made In

Evidence-based assessment relies on research and theory to inform the selection of constructs to be assessed for a specific assessment purpose, the methods and measures to be used in the assessment, and the manner in which the assessment process unfolds. An evidence-based approach to clinical assessment necessitates the recognition that, even when evidence-based instruments are used, the assessment process is a decision-making task in which hypotheses must be iteratively formulated and tested. In this chapter, we review (a) the progress that has been made in developing an evidence-based approach to clinical assessment in the past decade and (b) the many challenges that lie ahead if clinical assessment is to be truly evidence-based.

Discovery of five new Galactic symbiotic stars in the VPHAS+ survey

2021 ◽  
Vol 502 (2) ◽  
pp. 2513-2517
Author(s):  
Stavros Akras ◽  
Denise R Gonçalves ◽  
Alvaro Alvarez-Candal ◽  
Claudio B Pereira
Keyword(s):  
Spectroscopic Data ◽  
Selection Criterion ◽  
Optical Spectra ◽  
Emission Lines ◽  
High Rate ◽  
Symbiotic Stars ◽  
Selection Of

ABSTRACT We report the validation of a recently proposed infrared (IR) selection criterion for symbiotic stars (SySts). Spectroscopic data were obtained for seven candidates, selected from the SySt candidates of Akras et al. by employing the new supplementary IR selection criterion for SySts in the VST/OmegaCAM Photometric H-Alpha Survey. Five of them turned out to be genuine SySts after the detection of H α, He ii, and [O iii] emission lines as well as TiO molecular bands. The characteristic O vi Raman-scattered line is also detected in one of these SySts. According to their IR colours and optical spectra, all five newly discovered SySts are classified as S-type. The high rate of true SySts detections of this work demonstrates that the combination of the H α emission and the new IR criterion improves the selection of target lists for follow-up observations by minimizing the number of contaminants and optimizing the observing time.

scholarly journals A Clinical Study to Correlate the Facial Form and Maxillary Central Incisor Tooth Form in Males and Females of Davangere Population

2016 ◽  
Vol 04 (03) ◽  
pp. 156-164
Author(s):  
Deepak Bansal ◽  
Shruti Sharma ◽  
Manjit Kumar ◽  
Amrit Khosla
Keyword(s):  
Facial Appearance ◽  
Central Incisor ◽  
Incisor Tooth ◽  
Maxillary Central Incisor ◽  
Anterior Teeth ◽  
The Face ◽  
Tooth Form ◽  
Males And Females ◽  
Selection Of ◽  
Made In

AbstractAn altered facial appearance is more difficult to face, than problems related to ill-fitting denture or eating. The selection of maxillary anterior teeth for complete denture has long posed problem in clinical practice and a controversy about the best method to employ still exists. An attempt is made in the present study to clinically correlate the face form with maxillary central incisor tooth form in males and females of Davangere population. In 1914, Leon William's projected the “the form method” where he classified facial forms as square, tapering, and ovoid. Maxillary central incisors were selected according to the facial forms.Of total 100 subjects four different tooth forms and face forms were evaluated. They are: square, ovoid, square-tapered, tapered. No significant correlation existed between face form in male and females. Females exhibited greater correlation between face forms and inverted tooth form but that correlation is not sufficient to serve as a guide for selection of anterior teeth.

Dissecting quasars with the J-PAS narrow-band photometric survey

2019 ◽  
Vol 15 (S356) ◽  
pp. 12-16
Author(s):  
Silvia Bonoli ◽  
Giorgio Calderone ◽  
Raul Abramo ◽  
Jailson Alcaniz ◽  
Narciso Benitez ◽  
...  
Keyword(s):  
Emission Line ◽  
Wavelength Range ◽  
Software Package ◽  
Narrow Band ◽  
Active Galaxies ◽  
Emission Lines ◽  
Low Resolution ◽  
Strong Emission ◽  
Optical Wavelength ◽  
Quasar Spectra

AbstractThe J-PAS survey will soon start observing thousands of square degrees of the Northern Sky with its unique set of 56 narrow band filters covering the entire optical wavelength range, providing, effectively, a low resolution spectra for every object detected. Active galaxies and quasars, thanks to their strong emission lines, can be easily identified and characterized with J-PAS data. A variety of studies can be performed, from IFU-like analysis of local AGN, to clustering of high-z quasars. We also expect to be able to extract intrinsic physical quasar properties from the J-PAS pseudo-spectra, including continuum slope and emission line luminosities. Here we show the first attempts of using the QSFit software package to derive the properties for 22 quasars at 0.8 < z < 2 observed by the miniJPAS survey, the first deg2 of J-PAS data obtained with an interim camera. Results are compared with the ones obtained by applying the same software to SDSS quasar spectra.

New Development in High Efficiency Deep Grinding

2012 ◽  
Author(s):  
Andre D. L. Batako ◽  
Valery V. Kuzin ◽  
Brian Rowe
Keyword(s):  
Machine Tool ◽  
High Efficiency ◽  
Machining Process ◽  
Depth Of Cut ◽  
Removal Rates ◽  
Workpiece Surface ◽  
New Development ◽  
Cutting Processes ◽  
Selection Of ◽  
Made In

High Efficiency Deep Grinding (HEDG) has been known to secure high removal rates in grinding processes at high wheel speed, relatively large depth of cut and moderately high work speed. High removal rates in HEDG are associated with very efficient grinding and secure very low specific energy comparable to conventional cutting processes. Though there exist HEDG-enabled machine tools, the wide spread of HEDG has been very limited due to the requirement for the machine tool and process design to ensure workpiece surface integrity. HEDG is an aggressive machining process that requires an adequate selection of grinding parameters in order to be successful within a given machine tool and workpiece configuration. This paper presents progress made in the development of a specialised HEDG machine. Results of HEDG processes obtained from the designed machine tool are presented to illustrate achievable high specific removal rates. Specific grinding energies are shown alongside with measured contact arc temperatures. An enhanced single-pole thermocouple technique was used to measure the actual contact temperatures in deep cutting. The performance of conventional wheels is depicted together with the performance of a CBN wheel obtained from actual industrial tests.

scholarly journals Recent advances in the electrochemical construction of heterocycles

2014 ◽  
Vol 10 ◽  
pp. 2858-2873 ◽  
Author(s):  
Robert Francke
Keyword(s):  
Heterocyclic Compounds ◽  
Elevated Temperatures ◽  
Ring Formation ◽  
Environmentally Benign ◽  
Heterocyclic Chemistry ◽  
Ambient Conditions ◽  
Recent Developments ◽  
Strong Acids ◽  
Selection Of ◽  
Made In

Due to the fact that the major portion of pharmaceuticals and agrochemicals contains heterocyclic units and since the overall number of commercially used heterocyclic compounds is steadily growing, heterocyclic chemistry remains in the focus of the synthetic community. Enormous efforts have been made in the last decades in order to render the production of such compounds more selective and efficient. However, most of the conventional methods for the construction of heterocyclic cores still involve the use of strong acids or bases, the operation at elevated temperatures and/or the use of expensive catalysts and reagents. In this regard, electrosynthesis can provide a milder and more environmentally benign alternative. In fact, numerous examples for the electrochemical construction of heterocycles have been reported in recent years. These cases demonstrate that ring formation can be achieved efficiently under ambient conditions without the use of additional reagents. In order to account for the recent developments in this field, a selection of representative reactions is presented and discussed in this review.

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