scholarly journals Characterizing Long-term Optical Variability Properties of γ-Ray-bright Blazars

2021 ◽  
Vol 923 (1) ◽  
pp. 7
Author(s):  
Gopal Bhatta
Keyword(s):  
Flux Distribution ◽  
Optical Emission ◽  
Correlation Study ◽  
Optical Observations ◽  
Optical Data ◽  
Data Archives ◽  
Highly Correlated ◽  
Quasiperiodic Oscillations ◽  
Rule Out

Abstract Optical observations of a sample of 12 γ-ray-bright blazars from four optical data archives—American Association of Variable Star Observers, Small and Moderate Aperture Research Telescope System, Catalina, and Steward Observatory—are compiled to create densely sampled light curves spanning more than a decade. As a part of the blazar multiwavelength studies, several methods of analysis, e.g., flux distribution and rms–flux relation, are performed on the observations with the aim to compare the results with the similar ones in the γ-ray band presented in Bhatta & Dhital. It is found that, similar to the γ-ray band, blazars display significant variability in the optical band that can be characterized with lognormal flux distribution and a power-law dependence of rms on flux. It could be an indication of a possible inherent linear rms–flux relation, yet the scatter in the data does not allow to rule out other possibilities. When comparing variability properties in the two bands, the blazars in the γ-rays are found to exhibit stronger variability with a steeper possible linear rms–flux relation and a flux distribution that is more skewed toward higher fluxes. The cross-correlation study shows that except for source 3C 273, the overall optical and the γ-ray emission in the sources are highly correlated, suggesting a cospatial existence of the particles responsible for both the optical and γ-ray emission. Moreover, sources S5 0716+714, Mrk 421, Mrk 501, PKS 1424-418, and PKS 2155-304 revealed possible evidence of quasiperiodic oscillations in the optical emission with the characteristic timescales, which are comparable to those in the γ-ray band detected in our previous work.

scholarly journals Astrometric and Photometric Variability in Quasars

2009 ◽  
Vol 5 (S267) ◽  
pp. 103-103
Author(s):  
A. H. Andrei ◽  
S. Bouquillon ◽  
J. L. Penna ◽  
F. Taris ◽  
S. Anton ◽  
...  
Keyword(s):  
Strong Support ◽  
Optical Emission ◽  
Optical Observations ◽  
Massive Black Hole ◽  
Full Account ◽  
Photometric Variability ◽  
Central Engine ◽  
Relationship Of ◽  
The Relationship

Quasars are the choicest objects to define a quasi-inertial reference frame. At the same time, they are active galactic nuclei powered by a massive black hole. As the astrometric precision of ground-based optical observations approaches the limit set by the forthcoming GAIA mission, astrometric stability can be investigated. Though the optical emission from the core region usually exceeds the other components by a factor of a hundred, the variability of those components must surely imply some measure of variability of the astrometric baricenter. Whether this is confirmed or not, it puts important constraints on the relationship of the quasar's central engine to the surrounding distribution of matter. To investigate the correlation between long-term optical variability and what is dubbed as the “random walk” of the astrometric center, a program is being pursued at the WFI/ESO 2.2m. The sample was selected from quasars known to undergo large-amplitude and long-term optical variations (Smith et al. 1993; Teerikorpi 2000). The observations are typically made every two months. The treatment is differential, comparing the quasar position and brightness against a sample of selected stars for which the average relative distances and magnitudes remain constant. The provisional results for four objects bring strong support to the hypothesis of a relationship between astrometric and photometric variability. A full account is provided by Andrei et al. (2009).

scholarly journals Myopericytoma in the Antitragus of the Auricle: A Rare Tumor

2020 ◽  
pp. 014556132098457
Author(s):  
Tae Seong Eo ◽  
Jeong Hae Kie ◽  
Hyun Seung Choi ◽  
Junhui Jeong
Keyword(s):  
Large Firm ◽  
Rare Tumor ◽  
Long Term Follow Up ◽  
Slow Growing ◽  
Rule Out

A myopericytoma in the auricle is rare. If an auricle contains a large, firm, red-brown mass, excision should be considered because the mass may be a myopericytoma. After excision, histopathological and immunohistochemical diagnoses are essential to rule out malignancy. Long-term follow-up is required because the tumor is slow-growing.

scholarly journals Antioxidative and antimicrobial potentials of Parmelia saxatilis and Pseudoevernia furfuracea

2016 ◽  
pp. 9-18
Author(s):  
Jasmina Cilerdzic ◽  
Mirjana Stajic ◽  
Jelena Vukojevic
Keyword(s):  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
Side Effects ◽  
Klebsiella Pneumoniae ◽  
Bacterial Species ◽  
Phenol Content ◽  
Negative Side Effects ◽  
Highly Correlated ◽  
Ethanol Extracts

Even though numerous lichen species possess significant medical potentials they are still unexplored, and particularly species and strains originating from Serbia. Therefore, the aim of this study was to evaluate the antioxidative and antimicrobial potential of ethanol extracts of Parmelia saxatilis and Pseudoevernia furfuracea collected in Serbia. The tested extracts were good scavengers of DPPH radicals, with capacities ranging from 14.76% to 79.76% in P. saxatilis and from 21.39% to 90.04% in P. furfuracea. In P. saxatilis level of DPPH? neutralisation was highly correlated with phenol content (r2 = 0.9981) and in P. furfuracea with amount of total flavonoides (r2 = 0.9641). The extract of P. furfuracea inhibited the growth of all tested microorganisms with exception of Aspergillus flavus, while P. saxatilis extract affected only growth of bacterial species. Among tested microorganisms, Staphylococcus aureus and Klebsiella pneumoniae were the most sensitive, while Enterococcus faecalis, Pseudomonas aeruginosa as well as micromycetes were the least sensitive to tested extracts. Because of these potentials and the fact that their long term usage does not have any negative side effects on organism and development of microbial resistance, the extracts could be included in conventional therapy.

scholarly journals Snowpack variability and trends at long-term stations in northern Colorado, USA

2015 ◽  
Vol 371 ◽  
pp. 131-136 ◽  
Author(s):  
S. R. Fassnacht ◽  
M. Hultstrand
Keyword(s):  
Snow Depth ◽  
Snow Water Equivalent ◽  
Entire Period ◽  
Northern Colorado ◽  
Snow Water ◽  
Highly Correlated ◽  
The Individual

Abstract. The individual measurements from snowcourse stations were digitized for six stations across northern Colorado that had up to 79 years of record (1936 to 2014). These manual measurements are collected at the first of the month from February through May, with additional measurements in January and June. This dataset was used to evaluate the variability in snow depth and snow water equivalent (SWE) across a snowcourse, as well as trends in snowpack patterns across the entire period of record and over two halves of the record (up to 1975 and from 1976). Snowpack variability is correlated to depth and SWE. The snow depth variability is shown to be highly correlated with average April snow depth and day of year. Depth and SWE were found to be significantly decreasing over the entire period of record at two stations, while at another station the significant trends were an increase over the first half of the record and a decrease over the second half. Variability tended to decrease with time, when significant.

Custody of the Myelodysplastic Child: Implications for Selection for Early Treatment

PEDIATRICS ◽  
1974 ◽  
Vol 53 (2) ◽  
pp. 253-256
Author(s):  
Patricia W. Hayden ◽  
David B. Shurtleff ◽  
Arline B. Broy
Keyword(s):  
University Hospital ◽  
Contributory Factor ◽  
Foster Home ◽  
Term Care ◽  
Long Term Follow Up ◽  
Selection For ◽  
Foster Home Care ◽  
Highly Correlated ◽  
High Level

Of 173 patients with myelodysplasia followed in the Birth Defects Center at University Hospital between 1968 and 1972, 30 (17%) have been placed outside their natural families for temporary or long-term care. Only one has been adopted and five have been institutionalized; the remainder have been in foster home care. High level paralysis, mental retardation, and lower socioeconomic status correlate positively with placement. In this series, gender was not a contributory factor. An initial "hopeless" prognosis and/or selection for "no treatment" were decisions often made prior to referral to this center but were highly correlated to placement. Considering the multiple medical, emotional, and economic problems facing these families, relinquishment of custody should be anticipated in a significant percentage of cases. To date, placement outside the natural family has been viewed primarily as abandonment or as an emergency solution to a crisis. Long-term follow-up study of this group of children may indicate that transfer of custody can be a positive therapeutic alternative for the child and his family.

Justifying Too Much

2020 ◽  
pp. 419-434
Author(s):  
Bob Brecher
Keyword(s):  
Moral Theory ◽  
Long Term Consequences ◽  
Rule Out

In this chapter, I analyze the use and abuse of utilitarianism in the torture debate, arguing that the latter might turn out to be utilitarianism's nemesis. For what the debate lays bare is that, if we are to take utilitarianism seriously, then we must be prepared to torture the alleged terrorist's child, or indeed anyone at all, to prevent the so-called imminent catastrophe. Furthermore, if that conclusion is unpalatable on rule-utilitarian grounds—in terms of the institutional and long-term consequences of such a practice—then those same sorts of consideration rule out torturing the alleged terrorist themselves. That this is systematically obscured by those who would purport to justify interrogational torture by their being highly selective about the consequences they consider, and/or by arbitrarily “modifying” the scope of utilitarianism when it generates inconvenient conclusions, again suggests that utilitarianism may be fundamentally flawed; and that its use to defend interrogational torture shows this. The argument is in four sections: a refutation of the alleged necessity of interrogational torture in “ticking bomb” cases; an analysis of utilitarian proponents' of interrogational torture properly to understand that their utilitarianism cannot accommodate non-utilitarian limits when inconvenient; third, their failure to acknowledge the implications of that for the permissibility of torturing known innocents to force others to divulge information; and, fourth, how these considerations come together to suggest that utilitarianism might not be a moral theory at all.

scholarly journals Uncertainty Characterization and Propagation in the Community Long-Term Infrared Microwave Combined Atmospheric Product System (CLIMCAPS)

2019 ◽  
Vol 11 (10) ◽  
pp. 1227 ◽  
Author(s):  
Nadia Smith ◽  
Christopher D. Barnet
Keyword(s):  
Uncertainty Propagation ◽  
State Variables ◽  
Product System ◽  
Atmospheric Infrared Sounder ◽  
Cloud Properties ◽  
Infrared Measurements ◽  
Highly Correlated ◽  
Cross Track ◽  
Correlated Signals

The Community Long-term Infrared Microwave Combined Atmospheric Product System (CLIMCAPS) retrieves multiple Essential Climate Variables (ECV) about the vertical atmosphere from hyperspectral infrared measurements made by the Atmospheric InfraRed Sounder (AIRS, 2002–present) and its successor, the Cross-track Infrared Sounder (CrIS, 2011–present). CLIMCAPS ECVs are profiles of temperature and water vapor, column amounts of greenhouse gases (CO2, CH4), ozone (O3) and precursor gases (CO, SO2) as well as cloud properties. AIRS (and CrIS) spectral measurements are highly correlated signals of many atmospheric state variables. CLIMCAPS inverts an AIRS (and CrIS) measurement into a set of discrete ECVs by employing a sequential Bayesian approach in which scene-dependent uncertainty is rigorously propagated. This not only linearizes the inversion problem but explicitly accounts for spectral interference from other state variables so that the correlation among ECVs (and their uncertainty) may be minimized. Here, we outline the CLIMCAPS retrieval methodology with specific focus given to its sequential scene-dependent uncertainty propagation system. We conclude by demonstrating continuity in two CLIMCAPS ECVs across AIRS and CrIS so that a long-term data record may be generated to study the feedback cycles characterizing our climate system.

scholarly journals Optical observations of CI Cygni

1982 ◽  
Vol 70 ◽  
pp. 153-156
Author(s):  
N.A. Oliversen ◽  
C.M. Anderson ◽  
K.H. Nordsieck
Keyword(s):  
Emission Line ◽  
Optical Emission ◽  
Optical Observations

AbstractWe report optical emission line variations in CI Cygni during the 1980 eclipse.

scholarly journals To the matter of automatic stabilization of optical emission wavelength of He-Ne laser

2019 ◽  
Vol 124 ◽  
pp. 05028
Author(s):  
T.A. Akhmetshina ◽  
G.I. Il’in ◽  
A.G. Il’in ◽  
R.R. Fayzullin
Keyword(s):  
Gravitational Field ◽  
Block Diagram ◽  
Optical Emission ◽  
Automatic Stabilization ◽  
Automatic Mode ◽  
Neon Laser ◽  
Helium Neon Laser ◽  
Coherent Emission ◽  
Helium Neon

The work is devoted to solving problem of long-term synchronization of optical coherent emission of a helium-neon laser in the automatic mode, which can be used in particular in portable gravitational field detectors. A block diagram of the system that solves this problem is presented, the principle of operation is described. Much attention is also paid to existing solutions, their shortcomings are described.

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