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1. Introduction. Let S denote the family of functions f(z) regular and univalent in ∣z∣ < 1, with the expansion f(z) = z + a2z2 + … about z = 0, and let Af denote the area of the intersection of the open circle ∣ω∣ < 1 with Df, the image of ∣z∣ < 1 under f(z). A few years ago one of the authors (1) proved that if
A large radio continuum loop of diameter was discovered at G16.5+0.7 on the Bonn 2.7 GHz and NRO 10 GHz galactic plane surveys. The loop is associated with the H II region M16, and the diameter is 60 pc at a distance of 2.8 kpc. Figure 1 shows the loop at 2.7 GHz in gray scale. The spectrum is thermal and the total H II mass is estimated at 3×103 M⊙. If the loop is due to a shell of the same diameter, the mean electron density on the shell is about 4 cm−3. The total thermal energy is about 6×1048ergs. The characteristics are summarized in Table 1.
Radio observations with high sensitivity have shown that lots of more or less compact structures can be found in the field of extended and old supernova remnants (SNRs). These small diameter sources have been subject to many recent observations. The aim of these studies is to infer a possible physical association of these sources with the SNR shell. The interest in this link is based on various aspects, instabilities of shocked interstellar matter, star formation, etc.
Radio observations of large supernova remnants (SNRs) with high angular resolution have been provided by modern synthesis instruments preferentially at frequencies below 2 GHz. Since these instruments are sensitive mainly to unresolved emission spots, weak extended SNRs usually remain undetected. Besides this, there are numerous physical parameters, which can be studied more properly at higher frequencies. In particular, the polarization characteristics can be more easily analyzed and reduced to the intrinsic magnetic field orientation. In some cases foreground effects substantially disturb the SNR's field structure at low frequencies.
Changes of the cosmic ray electron spectrum throughout the Galaxy have been found, based on the comparison of large-scale radio continuum surveys. These observations are not compatible with the assumption of a static Galactic halo, but indicate the existence of a Galactic wind. Galactic plane surveys reveal sources of cosmic ray electrons in the Galactic disk. Recent studies of the population of radio sources show no evidence for a large number of compact Galactic non-thermal sources. Most of the extended sources are probably HII-regions. Relatively few new supernova remnants (SNRs) with low surface brightness could be identified. Most of the non-thermal emission in the disk-halo interface seems diffuse or unresolved, even at arcmin angular resolution.
We report the detection of a 4-kpc long, highly collimated radio feature emanating from the galactic center. This feature, which may be cylindrical in shape, is some 200 pc in diameter and extends almost perpendicular to the galactic plane. The structure may possibly be the remnant of a one-sided or highly asymmetric jet from the nucleus, or it might be a magnetic tornado produced by a twisted poloidal magnetic field between the disk and halo.
Symmetrical structures do exist, in the Galactic Centre region, In this article we attempt to summarize their properties and draw the attention of the scientific community to the advantages of taking them into account when working with models of the Centre of our Galaxy, Our work is corroborated by two new maps of the region at 10.7 GHz.
Data from the Effelsberg Galactic plane survey at 11 cm wavelength have been used to produce a survey of polarized intensity in the first Galactic quadrant. Besides polarized sources (Supernova remnants and extragalactic objects) extended polarized emission features are visible, which are not connected to distinct radio sources. To decide whether these features reflect characteristics of the local field or the distant spiral structure of the Galaxy we performed an integration of polarized intensities as a function of Galactic longitude. An anticorrelation with the thermal background component suggests a distance of more than 6 kpc for some components of the polarized emission. This enables us to derive an upper limit for the uniform component of the Galactic magnetic field.
The observation of an area of 120° × 56° centered on RA=8h DEC=20° at 408 MHz was the first astronomical use of the MPIfR 100-m telescope (1970) and was designed to compile a complete sky survey using also data from Jodrell Bank and Parkes (Haslam et al., 1982). The observation of the northern sky at 1420 MHz started in 1972 using the Stockert 25-m telescope and was finished in 1976 (Reich and Reich 1986). This survey has been completed to an all sky survey using data from Villa Elisa (Argentina). The two surveys are absolutely calibrated. The angular resolutions are 0.8° and 0.59°, respectively. A number of surveys of the Galactic plane have been made with the 100-m telescope at arc minute angular resolution. Surveys at 2695 MHz (|b| ≤ 5°) (Reich et al. 1990, Fürst et al. 1990) and at 1410 MHz (|b| < 4°) (Reich et al. 1990) are public.
At medium Galactic latitudes (up to |b| = 20°) the emission consists mainly of faint extended ridges or arcs superimposed on the still dominating, about 10 times stronger, diffuse Galactic emission. They have never been investigated in a systematic way although they provide important clues for the understanding of the “disk-halo connection”. This region is covered by new observations at 1400 MHz with the 100-m telescope.
We report multifrequency observations of the γ-ray blazar 0528+134 with the Effelsberg 100-m telescope, the IRAM 30-m telescope at Pico Veleta and the NRL Green Bank Interferometer. The observing methods are described elsewhere (Reich et al., 1993; Pohl et al., 1995). The radio lightcurves are given in Fig.1 in comparison to the status of 0528+134 in the EGRET energy range. The uncertainties in the flux densities quoted there are less than 5% at 10.55 GHz and lower frequencies, while slightly exceeding this value at 32 GHz and 86 GHz.
In this paper we present first results of a statistical analysis of correlated variability behaviour of flat-spectrum radio quasars (FSRQ) on the basis of EGRET data and cm-wavelength monitoring data. We use EGRET observations obtained between April 1991 to September 1993 and multifrequency radio observations at 2.8cm, 6cm and 11cm taken with the 100-m-Effelsberg Telescope parallel to the CGRO observations. In the following discussion the observed FSRQ which have not been detected by EGRET yet, are referred to as ‘candidates’ in contrast to the detected ones, called ‘EGRET-sources’. The methods used in this paper are described in more detail in Mücke et al. (1996).
Based on radio continuum surveys of the Galactic plane at wavelengths of 21 cm and 11 cm we have so far identified about 32 new supernova remnants in the area 357°.4 ≤ℓ≤ 76°. |b| ≤ 5°. This increases the number of known objects in this field by about 68%. Most of them are in the Galactic latitude range |b| 〉 0°.5. Some implications are discussed.
A radio continuum survey at medium Galactic latitudes with the 100−m telescope of the Max-Planck-Institut für Radioastronomie is being carried out at a center frequency of 1.4 GHz in total power and linear polarization. We present polarization and depolarization structures detected at medium latititudes with no corresponding observable structure in total power emission. Existence of such kind of polarization structures imply that the emission, due to the Faraday modulation of the Galactic synchrotron foreground, occurs in thin sheetlike regions. This phenomenon is a sign for fluctuating local magnetic field.
New radio continuum and spectral line observations of the Galactic radio source G18.95-1.1 are reported. The distance to G18.95-1.1 is 2 kpc as derived from HI-21 cm spectral line observations. These data also indicate an interaction with the interstellar medium. The radio continuum observations classify G18.95-1.1 as a composite supernova remnant.
Of all the methods available to observe magnetic fields in the Milky Way, the mapping of linear polarization at cm wavelengths has proven to be most successful. The instruments that have contributed most of the new data are the 100 m Effelsberg telescope and the Parkes 64 m dish. Their Galactic plane surveys gave us a new conception of the linear polarization distribution. A new Effelsberg 1.4 GHz ‘medium latitude polarization survey’ now being made gives us data about large sections of the Galaxy. Polarization maps of selected regions of the Galaxy are now being made at several frequencies up to 32 GHz. Data from Westerbork at ∼ 325 MHz, as well as data from the Canadian Galactic Plane Survey (CGPS) at 1.4 GHz give new exciting information.
We have observed 79 supernova remnants (SNRs) with the Urumqi 25 m telescope at λ6 cm during the Sino-German λ6 cm polarization survey of the Galactic plane. We measured flux densities of SNRs at λ6 cm, some of which are the first ever measured or the measurements at the highest frequency, so that we can determine or improve spectra of SNRs. Our observations have ruled out spectral breaks or spectral flattening that were suggested for a few SNRs, and confirmed the spectral break of S147. By combining our λ6 cm maps with λ11 cm and λ21 cm maps from the Effelsberg 100 m telescope, we calculated the spectral index maps of several large SNRs. For many remnants we obtained for the first time polarization images, which show the intrinsic magnetic field structures at λ6 cm. We disapproved three objects as being SNRs, OA184, G192.8−1.1 and G16.8−1.1, which show a thermal spectrum and no polarization. We have discovered two large supernova remnants, G178.2−4.2 and G25.1−2.3., in the survey maps.
The Sino-German λ6 cm polarization survey has mapped in total intensity and polarization intensity over an area of approximately 2200 square degrees in the Galactic disk. This survey provides an opportunity to search for Galactic supernova remnants (SNRs) that were previously unknown. We discovered the new SNRs G178.2−4.2 and G25.1−2.3 which have non-thermal spectra, using the λ6 cm data together with the observations with the Effelsberg telescope at λ11 cm and λ21 cm. Both G178.2−4.2 and G25.1−2.3 are faint and have an apparent diameter greater than 1°. G178.2−4.2 shows a polarized shell. HI data suggest that G25.1−2.3 might have a distance of about 3 kpc. The λ6 cm survey data were also very important to identify two other new SNRs, G152.4−2.1 and G190.9−2.2.
An external stress field, induced at the film edge of a nitride layer, affects the defect generation in the surface-near region. Nucleation and growth of oxide precipitates and/or the generation of dislocations result in the reduction of the width of the denuded zone. The defect formation is discussed in dependence on the stress, gettering technique (annealing conditions), and on the initial oxygen concentration. The effect on electrical parameters is shown. The investigations prove that an additional oxide film (SiO2/Si3N4 films) does not relax completely the tensile stress induced by the nitride layer.
After Prof. R. Wielebinski visited China in 1999, we started to plan the Sino-German λ6 cm polarization survey of the Galactic plane, using the Urumqi 25-m radio telescope of Xinjiang (formerly Urumqi) Astronomical Observatory, Chinese Academy of Sciences. It is a high-frequency complement of previous Effelsberg 21-cm and 11-cm surveys, using the same observing and processing methods. The telescope is located at an altitude of 2029 m above sea level at geographic longitude of 87°E and latitude 43°N. The dual-channel λ6 cm receiver with a polarimeter and a bandwidth of 600 MHz was designed by O. Lochner and constructed at the MPIfR in Germany with involvements by the Urumqi engineers M.Z. Chen and J. Ma. In August 2004, the receiver was installed at the secondary focus of the Urumqi 25-m telescope.
As evidenced by many of the chapters in this volume, robust research is emerging that explores the role of video games and virtual worlds in young people’s learning. However, far fewer studies have looked at the role of culture and community in relation to learning not only within these virtual spaces but also in the fan communities that surround them. Moreover, there are even fewer, if any, studies that explore these topics in the context of virtual worlds for very young children. This chapter addresses this gap through a focus on culture and community within and surrounding Webkinz World (WW), a virtual environment designed for children between the ages of six and thirteen.
While video games such as World of Warcraft and virtual worlds such as Second Life that target adolescents and adults have been popular for years, online environments aimed at preteen populations (between the ages of six and twelve) are a relatively new phenomenon. Recently, there has been a marked increase in the development of such spaces, with Webkinz World (www.webkinz.com), Club Penguin (www.clubpenguin.com), Neopets (www.neopets.com), and Barbie Girls (www.barbiegirls.com) among the most popular. These sites garner a significant number of monthly visitors, with Webkinz World attracting approximately twenty-eight million monthly visits in June 2009, Club Penguin and Neopets boasting approximately ten and ten and a half million, respectively, and Barbie Girls attracting nearly eight hundred and fifty thousand (Compete, Inc., 2009). Despite the rampant popularity of such sites, we know very little about children’s activities in these spaces at present.