scholarly journals The Abundances of Zinc and Copper in the Atmospheres of 78 Vir (A2p SrCrEu) and θ Leo (A2 IV)

2022 ◽  
Vol 6 (1) ◽  
pp. 15
Author(s):  
Richard Monier
Keyword(s):  
Spectral Synthesis ◽  
Convincing Evidence ◽  
Long Wavelength ◽  
Ultraviolet Spectra ◽  
Chemically Peculiar ◽  
Long Wave ◽  
Strong Transition

Abstract Zinc and Copper abundances are rarely available for normal and Chemically Peculiar A stars because the strongest transitions of Zn ii and Cu ii fall in the mid-UV. Estimates of the abundances of zinc and copper are derived for 78 Vir (A2p SrCrEu) and θ Leo (A2 IV) using mean mid-ultraviolet spectra constructed by coadding individual spectra collected with the Long Wave Prime and Long wavelength Redundant cameras over the 18 yr of the IUE mission. The strong transition of Cu ii at 2135.98 Å is present in 78 Vir and θ Leo but definitely stronger in 78 Vir, whereas all Zn ii lines are blended. Spectral synthesis of the least blended lines yields estimates of the abundances of zinc and copper of about 4.92 and 4.95 respectively in θ Leo and 5.82 and 5.19 in 78 Vir (on a scale where log(H) = 12). There is no convincing evidence that these lines varied in the spectra analyzed for both stars.

scholarly journals The Abundances of Cobalt and Nickel in the Atmosphere of 78 Vir (A2p SrCrEu)

2022 ◽  
Vol 6 (1) ◽  
pp. 9
Author(s):  
Richard Monier
Keyword(s):  
Convincing Evidence ◽  
Ultraviolet Spectrum ◽  
Rotational Period ◽  
Solar Abundance ◽  
Long Wavelength ◽  
Chemically Peculiar ◽  
Long Wave ◽  
Cobalt And Nickel

Abstract Cobalt and nickel abundances are rarely available for normal and Chemically Peculiar A stars because the strongest transitions of Co ii and Ni ii fall in the mid-UV. The abundances of cobalt and nickel are derived for 78 Vir using a mean mid-ultraviolet spectrum constructed by coadding 10 spectra collected with the Long Wave Prime and Long wavelength Redundant cameras over the 18 yr of the IUE mission. The strong transitions of Co ii at 2286.16 Å, 2307.86 Å, 2324.32 Å and 2580.33 Å and that of Ni ii et 2287.09 Å are present and more or less affected by blends. The least blended, λ 2286.16 Å, yields a mean overabundance of cobalt of 5 times the solar abundance, the Ni ii line at 2287.09 Å yields a 3 times solar overabundance. There is no convincing evidence that these lines varied in the spectra analyzed. The rotational period of 78 Vir estimated from its recent TESS lightcurve is 3.723 ± 0.055 days.

Long Wave-Length Buckling of Periodic Open-Cell Foams Subjected to Uniaxial Compression

2007 ◽  
Vol 345-346 ◽  
pp. 81-84
Author(s):  
Dai Okumura ◽  
Atsushi Okada ◽  
Nobutada Ohno
Keyword(s):  
Finite Element ◽  
Uniaxial Compression ◽  
Wave Length ◽  
Elastic Buckling ◽  
Element Analysis ◽  
Open Cell ◽  
Long Wavelength ◽  
Onset Condition ◽  
Long Wave ◽  
Open Cell Foams

In this study, the elastic buckling strength of cubic open-cell foams subjected to uniaxial compression is investigated using the homogenization framework developed by the present authors (Ohno et al., JMPS 2002; Okumura et al., JMPS 2004). First of all, based on the framework, the microscopic bifurcation and macroscopic instability of cubic open-cell foams are numerically analyzed by performing finite element analysis. It is thus shown that long wavelength buckling is the primary mode and occurs just after the onset of macroscopic instability. Then, a solution for predicting the stress of long wavelength buckling is analytically derived from the onset condition of macroscopic instability. The validity of this analytical solution is demonstrated by the finite element results.

On the stability of nonlinear waves coexisting with plasma beams

1975 ◽  
Vol 13 (1) ◽  
pp. 173-187 ◽  
Author(s):  
E. Infeld ◽  
G. Rowlands
Keyword(s):  
Nonlinear Wave ◽  
Growth Rates ◽  
Three Dimensional ◽  
Stationary Waves ◽  
One Dimensional ◽  
Long Wavelength ◽  
Long Wave ◽  
Set Up ◽  
The Stability ◽  
The One

In this paper we consider the stability of one-dimensional stationary waves set up by two counter-streaming beams of electrons in a background of stationary ions. The perturbations considered are long-wave in a direction perpendicular to the wave. The presence of a uniform magnetic field in the direction of the wave and the effect of a perpendicular pressure are taken into account. In the long-wavelength limit growth rates are diminished by the nonlinear wave. When the amplitude of this wave tends to its maximum value, the growth rates tend to zero. Thus the wave has a stabilizing effect for long-wave perturbations. Three- dimensional effects lead to additional instabilities which are also quenched by the nonlinear wave, but not as fast as the one-dimensional calculation indicates.

scholarly journals Concentration Fluctuation in Long Wavelength Limit in Liquid Magnesium Alloy

2011 ◽  
Vol 2 ◽  
pp. 47-49
Author(s):  
D Adhikari ◽  
B. P. Singh ◽  
I. S. Jha
Keyword(s):  
Order Parameter ◽  
Short Range ◽  
Short Range Order ◽  
Wave Length ◽  
Concentration Fluctuation ◽  
Chemical Order ◽  
Long Wavelength ◽  
Long Wave ◽  
Associated Solution Model ◽  
Associated Solution

The microscopic structure of MgSn liquid alloy at 1073K has been studied by using regular associated solution model. For this we have calculated the concentration fluctuation in long wave length limit [SCC(0)] and chemical short range order parameter (α1) of liquid MgSn alloy at 1073 K.Keywords: Binary Alloy; Complex; Chemical order; Microscopic FunctionThe Himalayan Physics Vol.2, No.2, May, 2011Page: 47-49Uploaded Date: 1 August, 2011

scholarly journals KELT-17: a chemically peculiar Am star and a hot-Jupiter planet

2020 ◽  
Vol 641 ◽  
pp. A145
Author(s):  
C. Saffe ◽  
P. Miquelarena ◽  
J. Alacoria ◽  
J. F. González ◽  
M. Flores ◽  
...  
Keyword(s):  
Spectral Synthesis ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
Balmer Line ◽  
Stellar Radius ◽  
Chemically Peculiar ◽  
Peculiar Stars ◽  
Chemical Pattern ◽  
Chemically Peculiar Stars ◽  
Hot Jupiter

Context. There is very little information to be found in the literature regarding the detection of planets orbiting chemically peculiar stars. Aims. Our aim is to determine the detailed chemical composition of the remarkable planet host star KELT-17. This object hosts a hot-Jupiter planet with 1.31 MJup detected by transits, and it is one of the more massive and rapidly rotating planet hosts seen to date. We set out to derive a complete chemical pattern for this star, in order to compare it with those of chemically peculiar stars. Methods. We carried out a detailed abundance determination in the planet host star KELT-17 via spectral synthesis. Stellar parameters were estimated iteratively by fitting Balmer line profiles and imposing the Fe ionization balance using the SYNTHE program together with plane-parallel ATLAS12 model atmospheres. Specific opacities for an arbitrary composition and microturbulence velocity vmicro were calculated through the opacity sampling (OS) method. The abundances were determined iteratively by fitting synthetic spectra to metallic lines of 16 different chemical species using SYNTHE. The complete chemical pattern of KELT-17 was compared to the recently published average pattern of Am stars. We estimated the stellar radius using two methods: a) comparing the synthetic spectral energy distribution with the available photometric data and the Gaia parallax, and b) using a Bayesian estimation of stellar parameters using stellar isochrones. Results. We found over-abundances of Ti, Cr, Mn, Fe, Ni, Zn, Sr, Y, Zr, and Ba, together with subsolar values of Ca and Sc. Notably, the chemical pattern agrees with those recently published for Am stars, making KELT-17 the first exoplanet host whose complete chemical pattern is unambiguously identified with this class. The stellar radius derived by two different methods agrees to each other and with those previously obtained in the literature.

The stellar content of 30 doradus derived from spatially integrated ultraviolet spectra: A test of spectral synthesis models

1995 ◽  
Vol 444 ◽  
pp. 647 ◽  
Author(s):  
William D. Vacca ◽  
Carmelle Robert ◽  
Claus Leitherer ◽  
Peter S. Conti
Keyword(s):  
Spectral Synthesis ◽  
Stellar Content ◽  
Ultraviolet Spectra ◽  
30 Doradus

Fluctuation Hydrodynamics, Thermophoresis of Nanoparticles and Heat Transfer in Nanofluids

2012 ◽  
Author(s):  
Alexandr S. Dmitriev
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Brownian Motion ◽  
Temperature Gradient ◽  
Long Wavelength ◽  
Long Wave ◽  
New Type ◽  
The One ◽  
Fluid Hydrodynamics ◽  
Two Fluid

In this paper we studied in the framework of two-fluid hydrodynamics with fluctuations the behavior of nanoparticles in the liquid with temperature gradient [1, 2]. It is shown that the acoustic long-wave fluctuations are not damped in liquids (long-wavelength phonons) and leads to an additional force acting on the nanoparticles, as well as lead to the emergence of a new force of thermophoresis [3], which is proportional to the temperature in three second degree. It is also shown that such a thermophoresis force arising under the two-fluid hydrodynamics, can lead to instability of an ensemble of nanoparticles in the presence of a temperature gradient. The last effect leads to the possible merger of the nanoparticles in the form of elongated clusters. The appearance of such clusters on the one hand, leads to an increase in effective thermal conductivity of nanofluids, and secondly, appearing elongated clusters contribute to the propagation of long-wavelength phonons along of such clusters. In fact, this new type of heat transfer in nanofluids, which must be considered in addition to the Brownian motion of nanoparticles.

scholarly journals A 3-D look into the atmosphere?

2009 ◽  
Vol 5 (H15) ◽  
pp. 151-160
Author(s):  
G. A. Wade ◽  
L. Mashonkina ◽  
T. Ryabchikova ◽  
J. Krticka ◽  
J. Silvester ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Spectral Synthesis ◽  
Surface Structures ◽  
Atmospheric Models ◽  
Physical Processes ◽  
Chemically Peculiar ◽  
Peculiar Stars ◽  
Stellar Pulsations ◽  
Magnetic Stars ◽  
Chemically Peculiar Stars

AbstractThe atmospheres of chemically peculiar stars can be highly structured in both the horizontal and vertical dimensions. While most prevalent in the magnetic stars, these structures can also exist in non-magnetic stars. In addition to providing an important window to understanding the physical processes at play in these complex atmospheres, they can also be exploited to study stellar pulsations. This article reviews contributions to the session “A 3D look into the atmosphere” of the Joint Discussion “Progress in understanding the physics of Ap and related stars”. It is divided into 3 sections: “Magnetic field and surface structures”, “Pulsations in the atmospheres of roAp stars/inversions”, and “Spectral synthesis/atmospheric models”.

scholarly journals Voltage-Tunable Mid- and Long-Wavelength Dual-Band Infrared Photodetector Based on Hybrid Self-Assembled and Sub-Monolayer Quantum Dots

Micromachines ◽  
2018 ◽  
Vol 10 (1) ◽  
pp. 4
Author(s):  
Yao Zhai ◽  
Guiru Gu ◽  
Xuejun Lu
Keyword(s):  
Quantum Dots ◽  
Dual Band ◽  
Band Selection ◽  
Infrared Photodetector ◽  
Long Wavelength ◽  
Long Wave ◽  
Self Assembled ◽  
Long Wave Infrared

In this paper, we report a mid-wave infrared (MWIR) and long-wave infrared (LWIR) dual-band photodetector capable of voltage-controllable detection band selection. The voltage-tunable dual-band photodetector is based on the multiple stacks of sub-monolayer (SML) quantum dots (QDs) and self-assembled QDs. By changing the photodetector bias voltages, one can set the detection band to be MWIR, or LWIR or both with high photodetectivity and low crosstalk between the bands.

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