Geometry of Hα Active Region Loops Observed on the Solar Disk

1983 ◽  
Vol 5 (2) ◽  
pp. 204-208 ◽  
Author(s):  
Chen Chuan-le ◽  
R. E. Loughhead
Keyword(s):  
Active Regions ◽  
Ground Level ◽  
Optical Observations ◽  
Large Array ◽  
Very Large Array ◽  
X Ray ◽  
The Past ◽  
Geometrical Shapes ◽  
Microwave Sources ◽  
Made In

Plasma loops are the dominant structures, in the higher levels of the Sun’s atmosphere above active regions. Much of our knowledge of their properties has come from space observations made over the past decade or so in the EUV and X-ray regions of the spectrum and, more recently, from high-resolution, two-dimensional images of microwave sources obtained with the Very Large Array radio interferometer (VLA). On the other hand, the spatial resolution of rocket and satellite observations has so far generally failed to match that of ground-level optical observations made in Hα and other strong chromospheric lines. The latter permit one to study in much greater detail the morphology of individual loops, as illustrated for example in the recent work of Loughhead, Wang and Blows (1983). These authors addressed themselves to the task of determining the true geometrical shapes of individual loops, a problem which had hitherto received little attention.

scholarly journals A Decade of Radio and X-ray Observations of SN 1993J

2005 ◽  
Vol 192 ◽  
pp. 3-11
Author(s):  
Schuyler D. Van Dyk ◽  
Kurt W. Weiler ◽  
Richard A. Sramek ◽  
Nino Panagia ◽  
Christopher Stockdale ◽  
...  
Keyword(s):  
Radio Emission ◽  
Radio Continuum ◽  
Large Array ◽  
Very Large Array ◽  
X Ray ◽  
Radio Frequencies ◽  
Made In ◽  
Circumstellar Medium

SummaryWe review ten years of radio continuum and X-ray monitoring of the Type IIb SN 1993J in M81. The supernova (SN) has been observed continuously, since only a few days after explosion, by our group with the Very Large Array at a number of radio frequencies, as well as by other groups. As a result, it is among the best-studied radio supernovae. The observed synchrotron radio emission is thought to arise from the interaction of the SN shock with the pre-SN wind-established circumstellar medium around the progenitor star. We describe the properties of the circumstellar interaction, based on the more fully-developed dataset, and compare this to our earlier characterization made in 1994. SN 1993J has also been a target of X-ray satellites, and we briefly discuss the nature of the X-ray emission and, together with the radio emission, describe the implications for the nature of the SN’s progenitor.

scholarly journals Quasi-simultaneous Radio/X-Ray Observations of the Candidate Transitional Millisecond Pulsar 3FGL J1544.6−1125 during its Low-luminosity Accretion-disk State

2021 ◽  
Vol 923 (1) ◽  
pp. 3
Author(s):  
Amruta D. Jaodand ◽  
Adam T. Deller ◽  
Nina Gusinskaia ◽  
Jason W. T. Hessels ◽  
James C. A. Miller-Jones ◽  
...  
Keyword(s):  
Accretion Disk ◽  
Radio Continuum ◽  
Continuum Emission ◽  
Large Array ◽  
Millisecond Pulsar ◽  
Very Large Array ◽  
X Ray ◽  
Upper Limit ◽  
5 Ghz ◽  
Variable Radio

Abstract 3FGL J1544.6−1125 is a candidate transitional millisecond pulsar (tMSP). Similar to the well-established tMSPs—PSR J1023+0038, IGR J18245−2452, and XSS J12270−4859—3FGL J1544.6−1125 shows γ-ray emission and discrete X-ray “low” and “high” modes during its low-luminosity accretion-disk state. Coordinated radio/X-ray observations of PSR J1023+0038 in its current low-luminosity accretion-disk state showed rapidly variable radio continuum emission—possibly originating from a compact, self-absorbed jet, the “propellering” of accretion material, and/or pulsar moding. 3FGL J1544.6−1125 is currently the only other (candidate) tMSP system in this state, and can be studied to see whether tMSPs are typically radio-loud compared to other neutron star binaries. In this work, we present a quasi-simultaneous Very Large Array and Swift radio/X-ray campaign on 3FGL J1544.6−1125. We detect 10 GHz radio emission varying in flux density from 47.7 ± 6.0 μJy down to ≲15 μJy (3σ upper limit) at four epochs spanning three weeks. At the brightest epoch, the radio luminosity is L 5 GHz = (2.17 ± 0.17) × 1027 erg s−1 for a quasi-simultaneous X-ray luminosity L 2–10 keV = (4.32 ± 0.23) × 1033 erg s−1 (for an assumed distance of 3.8 kpc). These luminosities are close to those of PSR J1023+0038, and the results strengthen the case that 3FGL J1544.6−1125 is a tMSP showing similar phenomenology to PSR J1023+0038.

High-resolution interstellar spectroscopy and star formation

1981 ◽  
Vol 303 (1480) ◽  
pp. 565-579 ◽  
Keyword(s):  
Star Formation ◽  
Molecular Clouds ◽  
Molecular Spectroscopy ◽  
Active Regions ◽  
Infrared Source ◽  
Very Large Array ◽  
Dark Clouds ◽  
The Past ◽  
Different Types ◽  
Interstellar Molecular Clouds

During the past several years, high spatial and spectral resolution molecular spectroscopy has greatly contributed to our knowledge of the physics, dynamics and chemistry of interstellar molecular clouds and thus has led to a better understanding of the conditions that lead to star formation. According to their physical properties, molecular clouds can be grouped into four different types: (i) the dark clouds, (ii) the molecular clouds associated with H+ regions, (iii) the ‘protostellar’ (or maser) environment, and (iv) the molecular envelopes of late-type stars. The first three types of cloud contain generally active regions of star formation. As typical examples the properties are discussed of individual clouds such as TMC 1 and L 183 for the cold clouds, S 140 and S 106 for the warm dark clouds with embedded infrared source, and Orion A for a region with associated H+ region. In S 140, NH 3 is clumped on a scale of not more than 20", whereas recent observations towards Orion A with the Very Large Array show that NH 3 clumps on a scale smaller than 5".

scholarly journals A Morphological and Histological Investigation of Imperfect Lungfish Fin Regeneration

2021 ◽  
Vol 9 ◽  
Author(s):  
Vivien Bothe ◽  
Igor Schneider ◽  
Nadia B. Fröbisch
Keyword(s):  
Tissue Regeneration ◽  
Molecular Mechanisms ◽  
Limb Regeneration ◽  
Body Parts ◽  
Serial Sections ◽  
Fin Regeneration ◽  
X Ray ◽  
The Past ◽  
Great Progress ◽  
Made In

Regeneration, the replacement of body parts in a living animal, has excited scientists for centuries and our knowledge of vertebrate appendage regeneration has increased significantly over the past decades. While the ability of amniotes to regenerate body parts is very limited, members of other vertebrate clades have been shown to have rather high regenerative capacities. Among tetrapods (four-limbed vertebrates), only salamanders show unparalleled capacities of epimorphic tissue regeneration including replacement of organ and body parts in an apparently perfect fashion. The closest living relatives of Tetrapoda, the lungfish, show regenerative abilities that are comparable to those of salamanders and recent studies suggest that these high regenerative capacities may indeed be ancestral for bony fish (osteichthyans) including tetrapods. While great progress has been made in recent years in understanding the cellular and molecular mechanisms deployed during appendage regeneration, comparatively few studies have investigated gross morphological and histological features of regenerated fins and limbs. Likewise, rather little is known about how fin regeneration compares morphologically to salamander limb regeneration. In this study, we investigated the morphology and histology of regenerated fins in all three modern lungfish families. Data from histological serial sections, 3D reconstructions, and x-ray microtomography scans were analyzed to assess morphological features, quality and pathologies in lungfish fin regenerates. We found several anomalies resulting from imperfect regeneration in regenerated fins in all investigated lungfish species, including fusion of skeletal elements, additional or fewer elements, and distal branching. The similarity of patterns in regeneration abnormalities compared to salamander limb regeneration lends further support to the hypothesis that high regenerative capacities are plesiomorphic for sarcopterygians.

scholarly journals FIBROUS DYSPLASIA OF BONES.

2020 ◽  
pp. 1-3
Author(s):  
M. Darrsana ◽  
Venkatachalam. K ◽  
Ampalaya Manu R ◽  
Haemanath P
Keyword(s):  
Fibrous Dysplasia ◽  
Bone Remodelling ◽  
X Rays ◽  
Endocrine Dysfunction ◽  
X Ray ◽  
The Past ◽  
Café Au Lait Spots ◽  
Gs Alpha ◽  
Topping Off ◽  
Made In

Fibrous dysplasia is an ailment , that can include , one or a few bones and is portrayed by bone deformations, pain and fractures, arising due to bone weakening. A few patients can also present with endocrine dysfunction ( precocious puberty) and cutaneous cafe '- au - lait spots.[1] Determination depends on X-ray assessment. Anticipation is to be surveyed with X-rays and markers of bone remodelling. A few newer comprehensions , of the patho - physiology have been made in the past I0 years. It is presently perceived that fibrous dysplasia is brought about , by a physical initiating transformation of the Gs alpha subunits , of the protein G, bringing about an expanded cAMP fixation and in this way, brings about anomalies of osteoblasts separation, and then subsequently these osteoblasts, creates abnormal bone. There is also an expansion in interleukin-6-initiated osteoclastic bone resorption, which forms the basis of reasoning, for treating these patients with bisphosphonates. In the previous 10 years, the bisphosphonate pamidronate has been utilized by imbuement for fibrous dysplasia (two courses for each year), with great outcomes regarding pain and, in about half of patients, the topping off of osteolytic sores.[2]

scholarly journals The Sun at the VLA's Metric and Decimetric Wavelengths

1990 ◽  
Vol 142 ◽  
pp. 523-524
Author(s):  
S. M. White ◽  
M. R. Kundu ◽  
N. Gopalswamy ◽  
E. J. Schmahl
Keyword(s):  
Large Scale ◽  
Dynamic Range ◽  
Active Regions ◽  
High Dynamic Range ◽  
The Sun ◽  
Large Array ◽  
Very Large Array ◽  
Preliminary Results ◽  
High Dynamic ◽  
Coronal Structures

During September 1988 (International Solar Month) we observed the Sun with the Very Large Array on 4 days in the period Sep. 11-17. The VLA was in its most compact configuration, which is ideal for studying large-scale coronal structures. Here we summarize some preliminary results of the observations at 0.333 and 1.5 GHz. Despite the presence of numerous active regions the Sun was actually very quiet, with no flares during our observing, and this allowed us to make high-dynamic-range maps.

scholarly journals Observations of Solar Active Regions at 2 and 6 cm Wavelengths with 3 Arc Second Resolution

1980 ◽  
Vol 86 ◽  
pp. 105-108
Author(s):  
T. Velusamy ◽  
M. R. Kundu
Keyword(s):  
Fine Structure ◽  
Active Regions ◽  
Field Of View ◽  
Large Array ◽  
The West ◽  
Very Large Array ◽  
Group I ◽  
West Limb ◽  
Solar Active Regions ◽  
Sunspot Groups

We have used the Very Large Array of the NRAO to observe solar active regions at 2 and 6 cm wavelengths in May 1979. In this paper we present and discuss the fine structure components of a sunspot associated radio region observed with a resolution of 3″ arc on May 4 and 5, 1979. In this region (McMath 15974) there were two distinct groups of sunspots separated by about 3′ arc. Group I located towards the west limb contained two spots while Group II in the east was a complex containing several spots that emerged during the period of our observations. At 6 cm both the sunspot groups were within the primary beam whereas at 2 cm only Group I was within the field of view. The VLA observations were made at 6 and 2 cm alternating between them every 5 minuts. The region was mapped with a resolution of about 3″ x 3″ using 10 hours of synthesis data on each day.

scholarly journals Very Large Array (VLA) Observations of Solar Active Regions

1980 ◽  
Vol 86 ◽  
pp. 109-117
Author(s):  
Kenneth R. Lang ◽  
Robert F. Willson
Keyword(s):  
Active Region ◽  
Solar Corona ◽  
Circular Polarization ◽  
Zeeman Effect ◽  
Active Regions ◽  
Large Array ◽  
Magnetic Dipoles ◽  
Very Large Array ◽  
Magnetic Structures ◽  
Brightness Temperatures

Very Large Array (VLA) synthesis maps of the total intensity and the circular polarization of three active regions at 6 cm wavelength are presented. The radiation from each active region is dominated by a few intense cores with angular sizes of ~ 0.5′, brightness temperatures of ~ 106 K, and degrees of circular polarization of 30 to 90%. Some of the core sources within a given active region exhibit opposite senses of circular polarization, suggesting the feet of magnetic dipoles, and the high brightness temperatures suggest that these magnetic structures belong to the low solar corona. We also present comparisons between our VLA maps of circular polarization and Zeeman effect magnetograms of the lower lying photosphere. There is an excellent correlation between the magnetic structures inferred by the two methods, indicating that synthesis maps of circular polarization at 6 cm can be used to delineate magnetic structures in the low solar corona.

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