scholarly journals The Role of Far-ultraviolet Pumping in Exciting the [O i] Lines in Protostellar Disks and Winds

2020 ◽  
Vol 904 (2) ◽  
pp. L27
Author(s):  
Ahmad Nemer ◽  
Jeremy Goodman ◽  
Lile Wang
Keyword(s):  
Protostellar Disks ◽  
Far Ultraviolet

scholarly journals The Origin of Jovian Planets in Protostellar Disks: The Role of Dead Zones

2003 ◽  
Vol 598 (1) ◽  
pp. 645-656 ◽  
Author(s):  
Soko Matsumura ◽  
Ralph E. Pudritz
Keyword(s):  
Dead Zones ◽  
Protostellar Disks ◽  
Jovian Planets

scholarly journals The Role of Flare Stars in Cosmic-ray Origin

1995 ◽  
Vol 151 ◽  
pp. 185-192
Author(s):  
Maurice M. Shapiro
Keyword(s):  
Alternative Hypothesis ◽  
Cosmic Ray ◽  
Optical Data ◽  
Seed Particles ◽  
Cosmic Ray Acceleration ◽  
The Galaxy ◽  
Flare Stars ◽  
Far Ultraviolet ◽  
Ultraviolet Observations

AbstractSupernovae and their expanding shock fronts are evidently the main agents of cosmic-ray acceleration. The thermal gas in the interstellar medium has been regarded as the reservoir of seed particles destined to become cosmic-ray nuclei. This assumption is, however, at variance with the source composition of galactic cosmic iays. In an alternative hypothesis, the seed particles are injected into the interstellar material as suprathermal seed ions, and it has been surmised that flare stars provide the initial boost. We find that the dMe and dKe stars are probably the principal sources of cosmic-ray seed particles. Most stars in the Galaxy are red dwarfs and many of these flares much more powerfully and frequently than solar flares. Augmenting the optical data, recent X-ray and far-ultraviolet observations now permit a better estimate of the energy budget. Altogether, dMe and dKe stars seem to be the most promising class of cosmic-ray injectors.

The role of disulfide bonds in the conformational stability and catalytic activity of phytase

2004 ◽  
Vol 82 (2) ◽  
pp. 329-334 ◽  
Author(s):  
Xiao-Yun Wang ◽  
Fan-Guo Meng ◽  
Hai-Meng Zhou
Keyword(s):  
Catalytic Activity ◽  
Disulfide Bonds ◽  
Conformational Stability ◽  
Three Dimensional ◽  
Fluorescence Emission ◽  
Dimensional Structure ◽  
Enzyme Activity Assay ◽  
First Order ◽  
Far Ultraviolet

Previous studies have predicted five disulfide bonds in Aspergillus niger phytase (phy A). To investigate the role of disulfide bonds, intrinsic fluorescence spectra, far-ultraviolet circular dichroism (CD) spectra, and an enzyme activity assay were used to compare the differences of catalytic activity and conformational stability of phytase during denaturation in urea in the presence and absence of dithiothreitol (DTT). In the presence of 2 mM DTT, the inactivation and unfolding were greatly enhanced at the same concentration of denaturant. The fluorescence emission maximum red shift and decreases of ellipticity at 222 nm were in accord with the changes of catalytic activity. The kinetics of the unfolding courses were a biphasic process consisting of two first-order reactions in the absence of DTT and a monophasic process of a first-order reaction in the presence of DTT. The results suggested that the loss of enzymatic activity was most likely because of a conformational change, and that disulfide bonds played an important role in three-dimensional structure and catalytic activity.Key words: phytase, urea denaturation, inactivation, disulfide bond.

scholarly journals A New View of the Solar Interface Region from the Interface Region Imaging Spectrograph (IRIS)

Solar Physics ◽  
2021 ◽  
Vol 296 (5) ◽  
Author(s):  
Bart De Pontieu ◽  
Vanessa Polito ◽  
Viggo Hansteen ◽  
Paola Testa ◽  
Katharine K. Reeves ◽  
...  
Keyword(s):  
Solar Atmosphere ◽  
Resonant Absorption ◽  
Interface Region ◽  
Machine Learning Techniques ◽  
Small Scale ◽  
Wide Range ◽  
Field Lines ◽  
Far Ultraviolet ◽  
Imaging Spectrograph

AbstractThe Interface Region Imaging Spectrograph (IRIS) has been obtaining near- and far-ultraviolet images and spectra of the solar atmosphere since July 2013. IRIS is the highest resolution observatory to provide seamless coverage of spectra and images from the photosphere into the low corona. The unique combination of near- and far-ultraviolet spectra and images at sub-arcsecond resolution and high cadence allows the tracing of mass and energy through the critical interface between the surface and the corona or solar wind. IRIS has enabled research into the fundamental physical processes thought to play a role in the low solar atmosphere such as ion–neutral interactions, magnetic reconnection, the generation, propagation, and dissipation of waves, the acceleration of non-thermal particles, and various small-scale instabilities. IRIS has provided insights into a wide range of phenomena including the discovery of non-thermal particles in coronal nano-flares, the formation and impact of spicules and other jets, resonant absorption and dissipation of Alfvénic waves, energy release and jet-like dynamics associated with braiding of magnetic-field lines, the role of turbulence and the tearing-mode instability in reconnection, the contribution of waves, turbulence, and non-thermal particles in the energy deposition during flares and smaller-scale events such as UV bursts, and the role of flux ropes and various other mechanisms in triggering and driving CMEs. IRIS observations have also been used to elucidate the physical mechanisms driving the solar irradiance that impacts Earth’s upper atmosphere, and the connections between solar and stellar physics. Advances in numerical modeling, inversion codes, and machine-learning techniques have played a key role. With the advent of exciting new instrumentation both on the ground, e.g. the Daniel K. Inouye Solar Telescope (DKIST) and the Atacama Large Millimeter/submillimeter Array (ALMA), and space-based, e.g. the Parker Solar Probe and the Solar Orbiter, we aim to review new insights based on IRIS observations or related modeling, and highlight some of the outstanding challenges.

scholarly journals 44. Astronomical Observations From Outside The Terrestrial Atmosphere

1976 ◽  
Vol 16 (3) ◽  
pp. 195-220
Author(s):  
A. D. Code
Keyword(s):  
Electromagnetic Spectrum ◽  
X Ray ◽  
Earth’S Atmosphere ◽  
The Earth ◽  
Accessible Region ◽  
Earth's Atmosphere ◽  
Far Ultraviolet ◽  
General Secretary ◽  
The Universe

Commission 44 is by title technique oriented. The following statement of the role of the commission was prepared for use by the General Secretary in responding to requests by non-astronomers with respect to the activities of IAU commissions.‘The Earth’s atmosphere is opaque to radiation throughout most of the electromagnetic spectrum. The light reaching the surface of the Earth from celestial objects is confined primarily to the visual region of the spectrum and a larger window in the radio region. Much of the infrared and all the far ultraviolet, X-ray and γ-ray radiation are absorbed in the upper atmosphere. Thus astronomers must carry their telescopes and auxiliary instrumentation above the Earth’s atmosphere to unlock the clues on the structure of the universe revealed by the light at these wavelengths. Furthermore the light in the accessible region of the spectrum that does reach the surface of the Earth is distorted and scattered in such a manner that the spatial resolution and details of the radiating source is seriously degraded.

Role of dactinomycin in the improved survival of children with Wilms' tumor

JAMA ◽  
1966 ◽  
Vol 195 (12) ◽  
pp. 1005-1009 ◽  
Author(s):  
D. J. Fernbach
Keyword(s):  
Wilms Tumor
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