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Compact Steep Spectrum (CSS) radio sources are defined as having straight steep spectra typical of extended double-lobed radio sources and structures unresolved by conventional interferometers (Peacock and Wall 1982; van Breugel et al., 1984; Fanti et al., 1985). Their spectra remain straight up to quite high frequencies, indicating that no dominant core is present. Sometimes the spectrum bends at frequencies lower than 1 GHz. The angular sizes imply projected linear sizes generally < 10 kpc.
The compact steep spectrum radio sources, 3C119, 3C287 and 3C343, are identified with QSO'S of redshift 0.46, 1.055 and 0.988 and visual magnitude 20.0, 17.7 and 20.6 respectively. The overall physical extent of each source is −500 pc (Fanti et al. 1985, 1986). Here we present the results of new global VLBI 18 cm observations which have been combined with MERLIN data to improve the U-V coverage. The data were mapped using the CALTECH and AIPS software packages and also using OLAF software system developed in Jodrell Bank for 3C119 and 3C343.
A large fraction of sources in flux limited radio samples consists of compact steep spectrum (CSS) sources (Fanti et al. 1987). These objects have their dominant emission on kiloparsec scales and are found in a variety of active galaxies, including Seyfert II's, peculiar galaxies and quasars. Observations of very nearby CSS sources have shown good correlations between their complex radio structures and optical emission-line gas suggesting violent interactions between jets and dense gas in their ambient interstellar media (van Breugel et al. 1984). Similar jet/gas interactions may occur in more distant and more powerful CSS sources.
The study of emoticon use in text communication is in its early stages (Aragon, Feldman, Chen & Kroll, 2014), with even less known about how emoticons function in multilingual environments. We describe a preliminary longitudinal analysis of text communication in an online bilingual scientific work environment and demonstrate how patterns of emoticon use constitute a novel yet systematic nonverbal aspect of communication. Specifically, coordination over bilingual speakers entails reductions in emoticon diversity over time that are greater for those who communicate in their L2 than in their L1. An analogous but weaker pattern is evident for lexical diversity in L2 but not L1. We hypothesize that reductions in emoticon diversity in the L2 are likely to reflect social contributions to alignment rather than purely proficiency.
We draw parallels between emoticons in textual communication and gesture in signed language with respect to the interdependence of codes by describing two contexts under which the behavior of emoticons in textual communication resembles that of gesture in speech. Generalizing from those findings, we propose that gesture is likely characterized by a nuanced interdependence with language whether signed, spoken or texted.
Objectives: Long-term follow-up of the Caries Management System (CMS) protocol demonstrated that regular monitoring and noninvasive management of dental caries is effective in reducing the number of caries-related events over a 7-year period. This analysis complements the authors’ original economic evaluation of the CMS by re-evaluating the per-protocol cost-effectiveness of the CMS approach.
Methods: An individual patient-simulation Markov model was developed previously, based on 3-year randomized-controlled trial (RCT) data, to simulate the incidence and progression of dental caries, and resultant interventions, and to evaluate the lifetime cost-effectiveness of the CMS versus standard dental care from the Australian private dental practitioner perspective (in which the baseline age distribution was similar to that of the Australian population). The 4-year posttrial follow-up data are used to re-evaluate the long-term cost-effectiveness of the CMS in a more real-life setting.
Results: The reduction in caries risk was maintained among those practices within which the CMS protocols were adhered to. The per-protocol model appears to be reasonably accurate at predicting the risk of restorative events in the posttrial follow-up period. The per-protocol lifetime cost per restorative event avoided is AUD1,980 (USD1,409; 1 AUD = 0.71 USD).
Conclusions: The current analysis confirms that the CMS approach is both effective, when the protocols are adhered to appropriately, and cost-effective compared with standard care in the Australian private practice setting.
We report on the results of a UV-Optical spectral monitoring of the bright Seyfert 1 galactic nuclei Mkn 335. This campaign began in June, 1989, and ended in June, 1991. Ultraviolet spectra of fourteen epochs at nearly uniform sampling of 30-day intervals, except when the object was inaccessible from the IUE satellite, have been obtained, of which twelve were coordinated with quasi-simultaneous ground-based optical observations made at Lick Observatory.
Acting as a pilot of the Square Kilometer Array (SKA), the Five hundred meter Aperture Spherical Telescope (FAST) has been proposed for construction in the unique karst area of southwest China. FAST is of Arecibo-type with rather a number of innovations, among which the active main spherical reflector shows fascinating. Furthermore, the feed cabin is supported and moved by cables controlled by computer, which avoids a heavy and expensive focal pointing system. With the effective aperture of 300 m, a large sky coverage, and a broad bandwidth (200 to 2000 MHz), possible capability up to 5 ∼8 GHz, FAST will be the world's largest single dish and perform markedly role in radio astronomy.
We present the nuclear structure of the radio galaxy 3C236 obtained by VLBI and MERLIN observations at both 1.663 and 5 GHz. Comparison with an HST WFPC-2 image of 3C236 suggests that the radio axis is at an angle of ∼ 30° to the plane of the sky, and 3C236 has an overall size of 4.5 Mpc and contains the longest jet known in the universe.
A meter-wave sky survey of the region north of declination +30°, excluding only four fields straddling the Galactic plane (each 8° × 8° in angular size), has been conducted with the Miyun Synthesis Radio Telescope operating at 232 MHz. The reduced Miyun General Catalogue contains 34,426 radio sources in total. To distinguish which sources were not observed by other sky surveys, we first identify sources in the MGC with those in the 6C (151 MHz) catalogue, using a matching radius of 100 arcseconds. The remaining MGC objects were then matched with the B2/B3 (408 MHz), 4C (178 MHz), Texas (365 MHz, 1400 MHz) and 87GB (4.85 GHz) catalogues. 6850 MGC sources were found to lack any radio counterpart in these reference catalogues. It means 19.9% of sources listed in the MGC are probably new.
One way to realize the Large radio Telescope with a collecting area approaching one square kilometer, continuously covering a frequency range between 200 MHz and 2 GHz, is to construct a passive spherical reflector array of about 30 individual unit telescopes, each ∼ 300 m diameter(Butcher 1995). Valleys amid the hills of southwest China would be ideal for such LT concept. We refer to this effort as the Kilometer-square Area Radio Synthesis Telescope project. Site surveying and Radio Interference monitoring looks promising. Engineering considerations are summarized.
We first very briefly introduce the major radio facilities for astronomical research in China, and then report on the present interference situation at major radio observatories. Some of the radio interference problems are caused by paging services, mobile phone satellites, telemetry services for power supply, waterpower and earthquake activity, or radar systems, but some causes are unknown. In the worst case, harmful to radio astronomy, the Sesan VLBI station has not been able to do any observations at 92 cm due to serious radio interference problems since 1992. Still more serious interference coming from satellites can be expected in the next decade. International efforts on frequency protection should be urgently pursued if ground-based radio astronomy is to survive.
We have carried out a series of measurements at some locations in Guizhou Province and one additional site at the Urumqi Astronomical Station in the Xinjiang autonomous region, to check on their suitability, from the point of view of interference, for the construction of a Five-hundred-meter Aperture Spherical Telescope (FAST). This large facility will in some sense act as a prototype for the Square Kilometer Array (SKA). Measurements were made using a commercial receiver in the frequency range 25–1500 MHz. The results in Guizhou look quite promising. A protected radio quiet zone in Guizhou would make it an ideal location for an international radio astronomical facility, and would establish the FAST site as a natural SKA location.
Radio astronomy has seen major advances in both instrumentation and scientific discovery during the last three years. This report is not encyclopedic but is intended to show the breadth of activity in the field. Division X is a technique-based division, and radio telescopes are becoming increasingly more international in character and usage. For these reasons this report devotes considerable attention to advances in instrumentation. More complete information on radio telescopes and scientific advances in the field can be found at the following Web site: http://www.stsci.edu/science/net-resources.html
The five hundred meter aperture spherical radio telescope is will use an active spherical reflector. When the zenith scan angle is changed, the illuminated part of the reflecting surface is made to fit a paraboloid of revolution in real time by active control. The maximum zenith scan angle | ψmax | of FAST is 30° under conditions of the geometry selected in order that the feed does not illuminate the ground. The result of this paper shows that the maximum zenith scan angle | ψmax | can be extended to 69° by offsetting the feed.
We present three epochs of VSOP observations of the BL Lac object 2007+777 at 5 GHz. Compared with the ground-based VLBA data, the space baselines with HALCA clearly reveal a more detailed and finer source structure. Mainly based on the quite uniform and circular UV-coverages of the VLBA, and using a new cross-selfcalibration method, we have found evidence for weak structural changes on a timescale of two weeks in the core region of this intraday variable source. The physical causes for these variations are discussed.
A Five hundred meter Aperture Spherical Telescope (FAST) is proposed to be built in the unique karst area of southwest China, and will act, in a sense, as a prototype for the Square Kilometer Array (SKA). It will be over twice as large as the Arecibo telescope coupled with much wider sky coverage. Some results from site surveys for such a SKA concept are briefly reported. Technically, FAST is not simply a copy of the existing Arecibo telescope but has rather a number of innovations. Firstly, the proposed main spherical reflector, by conforming to a paraboloid of revolution in real time through actuated active control, enables the realization of both wide bandwidth and full polarization capability while using standard feed design. Secondly, a feed support system which integrates optical, mechanical and electronic technologies will effectively reduce the cost of the support structure and control system. Pre-research on FAST has become a key project in the CAS.
VLBA polarimetric observations at 8.15 and 8.54 GHz of the quasar 3C 287 are presented and discussed. The source structure is complex, and the magnetic field geometry does not help in the interpretation of the source.
We report the observations of compact steep-spectrum radio sources (CSSs) by VLBI at 22 and 43 GHz and single dich at 22, 43, and 92 GHz. Our results show that CSS also has an active core as well as other AGNs.