A long-period radio transient active for three decades

Several long-period radio transients have recently been discovered, with strongly polarized coherent radio pulses appearing on timescales between tens to thousands of seconds^1,2. In some cases, the radio pulses have been interpreted as coming from rotating neutron stars with extremely strong magnetic fields, known as magnetars; the origin of other, occasionally periodic and less-well-sampled radio transients is still debated³. Coherent periodic radio emission is usually explained by rotating dipolar magnetic fields and pair-production mechanisms, but such models do not easily predict radio emission from such slowly rotating neutron stars and maintain it for extended times. On the other hand, highly magnetic isolated white dwarfs would be expected to have long spin periodicities, but periodic coherent radio emission has not yet been directly detected from these sources. Here we report observations of a long-period (21 min) radio transient, which we have labelled GPM J1839-10. The pulses vary in brightness by two orders of magnitude, last between 30 and 300 s and have quasiperiodic substructure. The observations prompted a search of radio archives and we found that the source has been repeating since at least 1988. The archival data enabled constraint of the period derivative to <3.6 × 10^-13 s s^-1, which is at the very limit of any classical theoretical model that predicts dipolar radio emission from an isolated neutron star.

A radio transient with unusually slow periodic emission

The high-frequency radio sky is bursting with synchrotron transients from massive stellar explosions and accretion events, but the low-frequency radio sky has, so far, been quiet beyond the Galactic pulsar population and the long-term scintillation of active galactic nuclei. The low-frequency band, however, is sensitive to exotic coherent and polarized radio-emission processes, such as electron-cyclotron maser emission from flaring M dwarfs¹, stellar magnetospheric plasma interactions with exoplanets² and a population of steep-spectrum pulsars³, making Galactic-plane searches a prospect for blind-transient discovery. Here we report an analysis of archival low-frequency radio data that reveals a periodic, low-frequency radio transient. We find that the source pulses every 18.18 min, an unusual periodicity that has, to our knowledge, not been observed previously. The emission is highly linearly polarized, bright, persists for 30-60 s on each occurrence and is visible across a broad frequency range. At times, the pulses comprise short-duration (<0.5 s) bursts; at others, a smoother profile is observed. These profiles evolve on timescales of hours. By measuring the dispersion of the radio pulses with respect to frequency, we have localized the source to within our own Galaxy and suggest that it could be an ultra-long-period magnetar.

GaLactic and Extragalactic All-sky Murchison Widefield Array survey eXtended (GLEAM-X) I: Survey Description and Initial Data Release

We describe a new low-frequency wideband radio survey of the southern sky. Observations covering 72-231MHz and Declinations south of +30° have been performed with the Murchison Widefield Array "extended" Phase I I configuration over 2018-2020 and will be processed to form data products including continuum and polarisation images and mosaics, multi-frequency catalogues, transient search data, and ionospheric measurements. From a pilot field described in this work, we publish an initial data release covering 1,447 deg² over 4 h≤ RA≤ 13 h, -32.7° ≤ Dec ≤ -20.7°. We process twenty frequency bands sampling 72-231 MHz, with a resolution of 2'-45″, and produce a wideband source-finding image across 170-231MHz with a root-mean-square noise of 1.27 ± 0.15 mJy beam^-1. Source-finding yields 79,124 components, of which 71,320 are fitted spectrally. The catalogue has a completeness of 98% at ~ 50 mJy, and a reliability of 98.2% at 5σ rising to 99.7% at 7σ. A catalogue is available from Vizier; images are made available on the GLEAM-X VO server and SkyView. This is the first in a series of data releases from the GLEAM-X survey.

Screwworm eradication program in Central America

The Screwworm Eradication Program has been extremely successful in its efforts to achieve its goal of eradication of screwworms through Central America and establishment of a permanent biological barrier in the eastern half of Panama. Following eradication of screwworms from Mexico in 1991, eradication was achieved in Belize in 1992, in Guatemala in 1993, and in El Salvador in 1994. Honduras has been free of screwworms since January 1995, and the number of cases in Nicaragua has dropped, as of April 1995, to about 4% of the average number of cases found during the period June-August 1993.

Liver fluke infections of cattle in Mali. An abattoir survey on prevalence and geographic distribution

Six hundred and ninety two cattle, slaughtered in various abattoirs in Mali between August 1983 and November 1984 were examined for evidence of Fasciola gigantica and Dicrocoelium hospes infections. A great variation in geographic prevalence was observed. Sufficient knowledge was acquired to demonstrate both the importance of fascioliasis in some areas and also the high prevalence of D. hospes in other areas. We suggest that the difference in prevalence from one geographic area to another is influenced by local climatic conditions, presence or absence of rivers and lakes, and differences in livestock management practices by various ethnic groups.

Education for health sciences/biomedical librarianship: past, present, future

This paper offers an analysis of and some predictions for the fields of library education and medical librarianship. The recent past of education for medical/health sciences librarianship is outlined, with emphasis on the changing nature of the library school, its faculty, and its students. The present situation is described, with specific reference to faculty, curriculum, and accreditation issues. A future agenda is proposed, identifying the need for interdisciplinary and cooperative efforts within the larger realms of medical informatics, high technology, a variety of health professions, and the community of contemporary library practice.

Elaeophorosis in sika deer in Texas

Elaeophora schneideri was found in sika deer (Cervus nippon) from several areas in Texas. The parasite produced unilateral tumorous masses on the head and/or feet. This is the first report of E. schneideri in Texas.

The use of pelleted dichlorvos in the control of murine acariasis

Dichlorvos resin pellets placed in bedding were found to be highly efficacious in eliminating Myobia musculi (Schrank) from a conventional mouse colony. The infested mice were exposed continuously to the insecticide for a 14-day period. At the end of this period no live mites or eggs were observed.