Witnessing history: a personal view of half a century in public health

Former Chief Medical Officer Sir Kenneth Calman recently celebrated 50 years in medicine. It was a period which saw the evolution of the public health agenda from communicable diseases to diseases of lifestyle, the change from a hospital-orientated health service to one dominated by community-based services, and the increasing recognition of inequalities as a major determinant of health. This paper documents selected highlights from his career including the Aberdeen typhoid outbreak, AIDS, bovine spongiform encephalopathy, foot and mouth disease, radioactive fallout, the invention of computerised tomography and magnetic resonance imaging, and draws parallels between the development of the modern understanding of public health and the theoretical background to the science 100 years earlier

Multifrequency VLA observations of the FR I radio galaxy 3C 31: morphology, spectrum and magnetic field

We present high-quality VLA images of the FR I radio galaxy 3C 31 in the frequency range 1365 to 8440 MHz with angular resolutions from 0.25 to 40 arcsec. Our new images reveal complex, well resolved filamentary substructure in the radio jets and tails. We also use these images to explore the spectral structure of 3C 31 on large and small scales. We infer the apparent magnetic field structure by correcting for Faraday rotation. Some of the intensity substructure in the jets is clearly related to structure in their apparent magnetic field: there are arcs of emission where the degree of linear polarization increases, with the apparent magnetic field parallel to the ridges of the arcs. The spectral indices are significantly steeper (0.62) within 7 arcsec of the nucleus than between 7 and 50 arcsec (0.52 - 0.57). The spectra of the jet edges are also slightly flatter than the average for their surroundings. At larger distances, the jets are clearly delimited from surrounding larger-scale emission both by their flatter radio spectra and by sharp brightness gradients. The spectral index of 0.62 in the first 7 arcsec of 3C 31's jets is very close to that found in other FR I galaxies where their jets first brighten in the radio and where X-ray synchrotron emission is most prominent. Farther from the nucleus, where the spectra flatten, X-ray emission is fainter relative to the radio. The brightest X-ray emission from FR I jets is therefore not associated with the flattest radio spectra, but with a particle-acceleration process whose characteristic energy index is 2.24. The spectral flattening with distance from the nucleus occurs where our relativistic jet models require deceleration, and the flatter-spectra at the jet edges may be associated with transverse velocity shear. (Slightly abridged)Comment: 17 pages, 13 figures, accepted for publication in MNRA

Farm dams in the wheatbelt

Of the estimated 76 000 farm dams in the wheatbelt, about 8 per cent either leak or are salt affected. The remaining 70 000 dams are capable of holding water for livestock use and can be regarded as sercicable dams. A great many of the serviceable dams are unreliable water supplies due to the combined effects of lack of runoff from catchments, shallow depth of storage and small size of storage in relation to expected demand from livestock and evaporation loss

Cost of farm water supplies : conclusions from surveys

The Department of Agriculture, in conjunction with the Farm Water Supply Advisory Committee, has conducted farm wster supply surveys in many districts in the wheatbelt. The aim of the surveys was to collect data to assess the existing water supplies, the potential for further water supply developments and to compare the relative difficulty of water supply development in different localities

Improved catchments for farm dams

The amounts and frequency of runoff from unimproved farmland catchments in Western Australia\u27s cereal and sheep districts are notoriously variable and unreliable. As a result many farmers have constructed improved catchments to ensure better reliability of farm dams for livestock and homestead water supplies. Improved catchments which are used extensively on these farms are all of the compacted or bare-earth type. These include roaded catchments, flat batter dams and, to a lesser extent, scraped catchments. This article mainly discusses roaded catchments, the most common of the improved catchment types on farms

West Midlands development : water supplies in the West Midlands

IF it is practical and economic to develop both surface and underground supplies, the aim on each farm should be to provide half the farm water requirement from dams, and the other half from bores

Structure of the magnetoionic medium around the FR Class I radio galaxy 3C 449

The goal of this work is to constrain the strength and structure of the magnetic field associated with the environment of the radio source 3C 449, using observations of Faraday rotation, which we model with a structure function technique and by comparison with numerical simulations. We assume that the magnetic field is a Gaussian, isotropic random variable and that it is embedded in the hot intra-group plasma surrounding the radio source. For this purpose, we present detailed rotation measure images for the polarized radio source 3C 449, previously observed with the Very Large Array at seven frequencies between 1.365 and 8.385 GHz. We quantify the statistics of the magnetic-field fluctuations by deriving rotation measure structure functions, which we fit using models derived from theoretical power spectra. We quantify the errors due to sampling by making multiple two-dimensional realizations of the best-fitting power spectrum.We also use depolarization measurements to estimate the minimum scale of the field variations. We then make three-dimensional models with a gas density distribution derived from X-ray observations and a random magnetic field with this power spectrum. Under these assumptions we find that both rotation measure and depolarization data are consistent with a broken power-law magnetic-field power spectrum, with a break at about 11 kpc and slopes of 2.98 and 2.07 at smaller and larger scales respectively. The maximum and minimum scales of the fluctuations are around 65 and 0.2 kpc, respectively. The average magnetic field strength at the cluster centre is 3.5 +/-1.2 micro-G, decreasing linearly with the gas density within about 16 kpc of the nucleus.Comment: 19 pages; 14 figures; accepted for publication on A&A. For a high quality version use ftp://ftp.eso.org/pub/general/guidetti