7,807 research outputs found
A 1.4 GHz radio continuum and polarization survey at medium Galactic latitudes: I. Observation and reduction technique
A radio continuum survey at medium Galactic latitudes with the Effelsberg
100-m telescope is being carried out at a centre frequency of 1.4 GHz in total
power and linear polarization. Areas up to +/- 20 degree of Galactic latitude
are now being observed at a sensitivity of 15 mK TB total intensity and 8 mK TB
in linear polarization with an angular resolution of 9'35. This paper describes
the observing and reduction technique applied which results in absolutely
calibrated maps. The methods are illustrated by examples of images from the
survey.Comment: 12 pages, 9 figures, Accepted for publication in Astronomy and
Astrophysics Supp. Se
Simultaneous microsurgical spermatic vein ligation and sclerotherapy - A combined procedure for the treatment of recurrent or persistent varicocele
Objectives: Microsurgical ligation as well as antegrade sclerotherapy have been established in varicocele treatment. The aim of this study was to evaluate whether a combination of microsurgery. and sclerotherapy can: provide a safe and effective treatment of varicocele recurrence or persistence. Methods. Nine patients with, recurrent or persistent varicoceles were operated by means of the combination method. Under microscopic control varix veins were ligated selectively preserving: lymphatics and arteries. Ectopic veins as a possible source for varicocele persistence or recurrence were also ligated. Finally, an intraoperative venography with subsequent sclerotherapy was, performed through one of the dissected veins. Results. Despite: difficult anatomical situations after previous surgical interventions, the operations were perform, ed successfully without any complications. Clinical controls showed varicocele disappearance without damage of the testis. No varicocele recurrence or persistence was observed. Conclusions. This method combines the advantages of both methods. Precision of the microsurgical technique is combined with velocity of sclerotherapy. Thus, it may represent an Interesting alternative to conventional operation methods especially in the treatment of recurrent or persistent varicoceles. Copyright (C) 2001 S. Karger AG, Basel
The sino-german 6cm polarization survey of the galactic plane: A summary
We have finished the 6cm polarization survey of the Galactic plane using the
Urumqi 25m radio telescope. It covers 10deg<l<230deg in Galactic longitude and
|b| <5deg in Galactic latitude. The new polarization maps not only reveal new
properties of the diffuse magnetized interstellar medium, but also are very
useful for studying individual objects such as Hii regions, which may act as
Faraday screens with strong regular magnetic fields inside, and supernova
remnants for their polarization properties and spectra. The high sensitivity of
the survey enables us to discover two new SNRs G178.2-4.2 and G25.3-2.1 and a
number of Hii regions.Comment: 10 pages, 1 figure. International Journal of Modern Physics:
Conference Series (IJMPCS) for Proceedings of 3rd Galileo-Xu Guangqi meetin
A Radio Continuum and Polarisation Study of the pulsar wind nebula CTB87 (G74.9+1.2)
We present radio continuum and linear polarisation observations of the pulsar
wind nebula CTB87 (G74.9+1.2) with the Effelsberg 100-m radio telescope between
4.75 and 32 GHz. An analysis of these new data including archived low-frequency
observations at 1420 MHz and 408 MHz from the Canadian Galactic Plane Survey
shows that CTB87 consists of two distinct emission components: a compact
kidney-shaped component, 14 pc x 8.5 pc (7.8' x 4.8') in size and a larger
diffuse, spherical and centrally peaked component of about 30 pc (17') in
diameter. The kidney-shaped component with a much steeper radio continuum
spectrum is highly linearly polarised and likely represents a relic pulsar wind
nebula. The diffuse component represents the undisturbed part of the PWN
expanding inside a cavity or stellar wind bubble. The previously reported
spectral break above 10 GHz is likely the result of missing large-scale
emission and insufficient sensitivity of the high-frequency radio continuum
observations. The simulation of the system's evolution yields an age of about
18,000 years as the result of a type II supernova explosion with an ejecta mass
of about 12 solar masses and an explosion energy of about 7 x 10^50 erg. We
also found evidence for a radio shell in our polarisation data which represents
the blast wave that entered the molecular cloud complex at a radius of about 13
pc.Comment: 17 pages, 15 figures, 5 tables, MNRAS, accepted for publicatio
Implementation of an Online Feedback-Path-Modelling Active Noise Control System
Active Noise Control (ANC) systems have proved to be a very efficient way to reduce low-frequency acoustic noise. On this domain, passive techniques like enclosures, barriers and silencers tend to be relatively large, costly and ineffective. Although many studies and articles have been published in order to improve performance and stability, the implementation of a real-time, stable and robust system still faces several theoretical and practical challenges
Faint HI 21-cm Emission Line Wings at Forbidden-Velocities
We present the results of a search for faint HI 21-cm emission line wings at
velocities forbidden by Galactic rotation in the Galactic plane using the
Leiden/Dwingeloo HI Survey data and the HI Southern Galactic Plane Survey data.
These ``forbidden-velocity wings (FVWs)'' appear as protruding excessive
emission in comparison with their surroundings in limited (< 2 deg) spatial
regions over velocity extent more than ~20 km/s in large-scale (l-v) diagrams.
Their high-velocities imply that there should be some dynamical phenomena
associated. We have identified 87 FVWs. We present their catalog, and discuss
their distribution and statistical properties. We found that 85% of FVWs are
not coincident with known supernova remnants (SNRs), galaxies, or high-velocity
clouds. Their natures are currently unknown. We suspect that many of them are
fast-moving HI shells and filaments associated with the oldest SNRs that are
essentially invisible except via their HI line emission. We discuss other
possible origins.Comment: 41 pages, 14 figures, to be published in apj
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