scholarly journals Use of CCDs in Schmidt Telescopes for the Investigation of Hα Emission of Flare Stars

1995 ◽  
Vol 148 ◽  
pp. 60-64
Author(s):  
Gábor Szécsényi-Nagy
Keyword(s):  
Open Clusters ◽  
Good Resolution ◽  
Focal Surface ◽  
Stellar Flares ◽  
Recent Developments ◽  
Traditional Mode ◽  
Hα Emission ◽  
Flare Stars ◽  
Characteristic Features ◽  
Silicon Based

AbstractThe use of Schmidt telescopes in their traditional mode for the detection of stellar flares and for the UV and PG photometry of these stars proved to be very productive. The fast optical system and reliable sensitivity of modern photographic emulsions resulted in a photometric time-resolution of several minutes even in the case of distant objects. One of the most important characteristics of flare stars may be the tendency for coexistence with more massive and more luminous member stars of young stellar aggregates (mainly open clusters). Although the vast majority of flare stars discovered seem to belong to clusters, a great many of them are neighbours of our sun. These can be investigated in depth because a sufficient number of their photons can be collected and recorded in narrow photometric bands or even in spectra of good resolution. The direct comparison of solar vicinity flare stars with flare-active members of distant clusters has been almost impossible. However recent developments in silicon-based photon-detecting technology offer the advantage of incredibly high detector quantum efficiency (DQE) in many spectral regions where photographic materials never reached an acceptable level. Hα emission is one of the most characteristic features of flare stars, and the wavelength of Hα photons fits extremely well with the peak of the spectral sensitivity curves of silicon photon detectors. CCD chips placed in the focal surface of Schmidt telescopes seem to be very promising for the future investigation of Hα emission of flare stars.

scholarly journals Flare stars in nearby Galactic open clusters based on TESS data

2021 ◽  
Vol 51 (1) ◽  
Author(s):  
O. Maryeva ◽  
K. Bicz ◽  
C. Xia ◽  
M. Baratella ◽  
P. Čechvala ◽  
...  
Keyword(s):  
Open Clusters ◽  
Flare Stars

scholarly journals X-Ray Emission from Stellar Flares: Exosat Results

1989 ◽  
Vol 104 (2) ◽  
pp. 17-20 ◽  
Author(s):  
R. Pallavicini ◽  
G. Tagliaferri
Keyword(s):  
Main Sequence ◽  
Late Type ◽  
X Ray ◽  
Visual Binary ◽  
Stellar Flares ◽  
Flare Stars ◽  
M Dwarf

AbstractWe present an overview of recent observations of stellar X-ray flares obtained with the EXOSAT Observatory. We discuss a few examples of flares from M dwarf flare stars, from RS CVn and Algol-type binaries, from single late-type stars (including a G0 dwarf and an A-type visual binary), and from pre-main-sequence objects. We also draw some general conclusions from the pieliminary analysis of the EXOSAT data sample.

Recent developments in amorphous silicon-based solar cells

1996 ◽  
Vol 194 (1) ◽  
pp. 41-53 ◽  
Author(s):  
C. Beneking ◽  
B. Rech ◽  
J. Fölsch ◽  
H. Wagner
Keyword(s):  
Solar Cells ◽  
Amorphous Silicon ◽  
Recent Developments ◽  
Silicon Based

Impact of Hydrogen Implantation on Helium Implantation Induced Defects

2005 ◽  
Vol 108-109 ◽  
pp. 309-314 ◽  
Author(s):  
G. Gaudin ◽  
Frédéric Cayrel ◽  
Corrado Bongiorno ◽  
Robert Jérisian ◽  
Vito Raineri ◽  
...  
Keyword(s):  
Cavity Growth ◽  
High Dose ◽  
Defect Band ◽  
Hydrogen Addition ◽  
Recent Developments ◽  
Hydrogen Implantation ◽  
Helium Implantation ◽  
Silicon Based ◽  
Induced Defects ◽  
The Impact

Silicon-based power device performances are largely affected by metal contamination occurring during device manufacturing. Among the usual gettering techniques, recent developments were done on high dose helium implantation. Even though the gettering efficiency of this technique has been demonstrated in device application, the required doses are still extremely high for an industrial application. Recently, it has been shown that the use of H/He co-implantation limits the total requested doses [1]. In this paper, co-implantation of H/He, which has been already used to reduce the dose in the smart-cut® process is explored. The goal of this work is to decrease efficiently the implanted dose maintaining an efficient metallic gettering without degrading the Si surface. The impact of H implantation on He implantation induced defects is carefully studied. The TEM observations have evidenced that hydrogen addition drastically modified the defect band structure and promotes the cavity growth.. Additionally, we demonstrate that an efficient gettering can be obtained.

Recent Developments in Silicon-based MEMS Photonic Systems

2007 ◽  
Author(s):  
W. Noell ◽  
N.F. de Rooij ◽  
M. Epitaux ◽  
R. Hauffe ◽  
T. Overstolz ◽  
...  
Keyword(s):  
Recent Developments ◽  
Silicon Based

Li production by stellar flares in young open clusters

2008 ◽  
Vol 52 (7-10) ◽  
pp. 423-426 ◽  
Author(s):  
V. Tatischeff ◽  
J.-P. Thibaud
Keyword(s):  
Open Clusters ◽  
Stellar Flares

Silicon-Based Reagents for Difluoromethylation and Difluoromethylenation Reactions

Synthesis ◽  
2017 ◽  
Vol 49 (15) ◽  
pp. 3394-3406 ◽  
Author(s):  
Sankarganesh Krishnamoorthy ◽  
G. Prakash
Keyword(s):  
Nucleophilic Substitution ◽  
Oxidative Coupling ◽  
Nucleophilic Addition ◽  
Cross Coupling ◽  
Terminal Alkynes ◽  
Group Transfer ◽  
Recent Developments ◽  
Perfluoroalkyl Group ◽  
Activation Conditions ◽  
Silicon Based

There have been significant developments in the area of perfluoroalkyl group transfer using silicon reagents, specifically in nucleo­philic trifluoromethylation. The mild and versatile activation conditions bestow significant synthetic prowess to the silicon reagents in the area of fluoroalkylations. Owing to the importance of difluoromethylene (CF2) containing compounds in pharmaceuticals, materials, and agrochemicals, several CF2 group transfer methods using related silicon reagents have been developed and studied in detail. This review summarizes the recent developments and trends in this area.1 Introduction2 Trimethyl(trifluoromethyl)silane (Me3SiCF3)3 (Difluoromethyl)trimethylsilane (Me3SiCF2H)3.1 Nucleophilic Addition3.2 Nucleophilic Substitution3.3 Nucleophilic Difluoromethylation of Electron-Deficient Hetero­cycles3.4 Metal-Mediated Cross Coupling3.5 Oxidative Coupling of Terminal Alkynes4 Post-functionalizable Difluoromethyl Transfer Reagents4.1 (Chlorodifluoromethyl)trimethylsilane (Me3SiCF2Cl)4.2 (Bromodifluoromethyl)trimethylsilane (Me3SiCF2Br)4.3 [Difluoro(iodo)methyl]trimethylsilane (Me3SiCF2I)4.4 [Difluoro(phenylthio)methyl]trimethylsilane (Me3SiCF2SPh)4.5 [Difluoro(phenylsulfonyl)methyl]trimethylsilane (Me3SiCF2SO2Ph)4.6 Diethyl [Difluoro(trimethylsilyl)methyl]phosphonate [Me3SiCF2P(O)(OEt)2]4.7 Ethyl Difluoro(trimethylsilyl)acetate (Me3SiCF2CO2Et)4.8 Difluoro(trimethylsilyl)acetamides (Me3SiCF2CONR2)4.9 Difluoro(trimethylsilyl)acetonitrile (Me3SiCF2CN)5 Others6 Conclusions

scholarly journals Stellar Chromospheric Variability

Universe ◽  
2021 ◽  
Vol 7 (11) ◽  
pp. 440
Author(s):  
Richard de de Grijs ◽  
Devika Kamath
Keyword(s):  
Large Scale ◽  
Binary Systems ◽  
Magnetic Activity ◽  
Close Binary ◽  
Physical Parameters ◽  
Stellar Rotation ◽  
Chromospheric Activity ◽  
Recent Developments ◽  
Hα Emission ◽  
Activity Cycles

Cool stars with convective envelopes of spectral types F and later tend to exhibit magnetic activity throughout their atmospheres. The presence of strong and variable magnetic fields is evidenced by photospheric starspots, chromospheric plages and coronal flares, as well as by strong Ca ii H+K and Hα emission, combined with the presence of ultraviolet resonance lines. We review the drivers of stellar chromospheric activity and the resulting physical parameters implied by the observational diagnostics. At a basic level, we explore the importance of stellar dynamos and their activity cycles for a range of stellar types across the Hertzsprung–Russell diagram. We focus, in particular, on recent developments pertaining to stellar rotation properties, including the putative Vaughan–Preston gap. We also pay specific attention to magnetic variability associated with close binary systems, including RS Canum Venaticorum, BY Draconis, W Ursae Majoris and Algol binaries. At the present time, large-scale photometric and spectroscopic surveys are becoming generally available, thus leading to a resurgence of research into chromospheric activity. This opens up promising prospects to gain a much improved understanding of chromospheric physics and its wide-ranging impact.

scholarly journals Recent Developments in the Use of Glyconanoparticles and Related Quantum Dots for the Detection of Lectins, Viruses, Bacteria and Cancer Cells

2021 ◽  
Vol 9 ◽  
Author(s):  
Pedro J. Hernando ◽  
Simone Dedola ◽  
María J. Marín ◽  
Robert A. Field
Keyword(s):  
Quantum Dots ◽  
Cancer Cells ◽  
Semiconductor Quantum Dots ◽  
The Past ◽  
Coated Nanoparticles ◽  
Gold Silver ◽  
Recent Developments ◽  
Protein Toxins ◽  
Silicon Based

Carbohydrate-coated nanoparticles—glyconanoparticles—are finding increased interest as tools in biomedicine. This compilation, mainly covering the past five years, comprises the use of gold, silver and ferrite (magnetic) nanoparticles, silicon-based and cadmium-based quantum dots. Applications in the detection of lectins/protein toxins, viruses and bacteria are covered, as well as advances in detection of cancer cells. The role of the carbohydrate moieties in stabilising nanoparticles and providing selectivity in bioassays is discussed, the issue of cytotoxicity encountered in some systems, especially semiconductor quantum dots, is also considered. Efforts to overcome the latter problem by using other types of nanoparticles, based on gold or silicon, are also presented.

scholarly journals Flare Stars in Star Clusters and Associations

1975 ◽  
Vol 67 ◽  
pp. 1-14 ◽  
Author(s):  
V. A. Ambartsumian ◽  
L. V. Mirzoyan
Keyword(s):  
Stellar Evolution ◽  
Star Clusters ◽  
Open Clusters ◽  
Point Of View ◽  
Flare Activity ◽  
Theoretical Point ◽  
Star Clusters And Associations ◽  
Stellar Flare ◽  
Dwarf Stars ◽  
Flare Stars

The study of stellar evolution can be undertaken either from a purely theoretical point of view or from a more observational approach. The present standpoint is the second one. It starts from the concepts of stellar evolution in associations and open clusters and from stellar flare activity. Statistical considerations show that flare activity is a regular stage in the evolution of stars through which all the dwarf stars go.

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