How to keep farm accounts

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Milk production costs and milk prices

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Analysis of travelling waves associated with the modelling of aerosolised skin grafts

A previous model developed by the authors investigates the growth patterns of keratinocyte cell colonies after they have been applied to a burn site using a spray technique. In this paper, we investigate a simplified one-dimensional version of the model. This model yields travelling wave solutions and we analyse the behaviour of the travelling waves. Approximations for the rate of healing and maximum values for both the active healing and the healed cell densities are obtained

Can Reflection from Grains Diagnose the Albedo?

By radiation transfer models with a realistic power spectra of the projected density distributions, we show that the optical properties of grains are poorly constrained by observations of reflection nebulae. The ISM is known to be hierarchically clumped from a variety of observations (molecules, H I, far-infrared). Our models assume the albedo and phase parameter of the dust, the radial optical depth of the sphere averaged over all directions, and random distributions of the dust within the sphere. The outputs are the stellar extinction, optical depth, and flux of scattered light as seen from various viewing angles. Observations provide the extinction and scattered flux from a particular direction. Hierarchical geometry has a large effect on the flux of scattered light emerging from a nebula for a particular extinction of the exciting star. There is a very large spread in both scattered fluxes and extinctions for any distribution of dust. Consequently, an observed stellar extinction and scattered flux can be fitted by a wide range of albedos. With hierarchical geometry it is not completely safe to determine even relative optical constants from multiwavelength observations of the same reflection nebula. The geometry effectively changes with wavelength as the opacity of the clumps varies. Limits on the implications of observing the same object in various wavelengths are discussed briefly. Henry (2002) uses a recipe to determine the scattered flux from a star with a given extinction. It is claimed to be independent of the geometry. It provides considerably more scattering than our models, probably leading to an underestimate of the grain albedos from the UV Diffuse Galactic Light.Comment: 27 pages, including 7 figures. Accepted by Ap

Introduced birds in urban remnant vegetation : does remnant size really matter?

Introduced birds are a pervasive and dominant element of urban ecosystems. We examined the richness and relative abundance of introduced bird species in small (1&ndash;5 ha) medium (6&ndash;15 ha) and large (&gt;15 ha) remnants of native vegetation within an urban matrix. Transects were surveyed during breeding and non-breeding seasons. There was a significant relationship between introduced species richness and remnant size with larger remnants supporting more introduced species. There was no significant difference in relative abundance of introduced species in remnants of different sizes. Introduced species, as a proportion of the relative abundance of the total avifauna (native and introduced species), did not vary significantly between remnants of differing sizes. There were significant differences in the composition of introduced bird species between the different remnant sizes, with large remnants supporting significantly different assemblages than medium and small remnants. Other variables also have substantial effects on the abundance of introduced bird species. The lack of significant differences in abundance between remnant sizes suggests they were all equally susceptible to invasion. No patches in the urban matrix are likely to be unaffected by introduced species. The effective long-term control of introduced bird species is difficult and resources may be better spent managing habitat in a way which renders it less suitable for introduced species (e.g. reducing areas of disturbed ground and weed dominated areas).<br /

Radio sources at low Galactic latitudes

We present high-resolution radio observations of a sample of 65 radio sources at low Galactic latitudes. The sources were all observed at 5 GHz with the Very Large Array A-array. MERLIN observations at 5 GHz of the ultracompact HII region G34.26+0.15 and one of the extragalactic sources, B1857-000, are also presented, as are GMRT observations of HI in the direction of three sources, B1801-203, B1802-196 and B1938+229. These observations were made with the objectives of (i) finding compact components suitable for studying the effects of interstellar scattering at lower frequencies, (ii) identifying high surface-brightness lobes of background radio sources to probe the Galactic magnetic field on different scales via polarization observations, and (iii) searching for young supernova remnants. We discuss the nature of the sources found to have shell or shell-like structure and exhibiting both thermal and non-thermal spectra. Of the remaining sources, B1749-281 is coincident within the positional errors of a known pulsar, not detected earlier at 5 GHz. The rest are likely to be background extragalactic objects.Comment: 12 pages, 6 figures (most with multiple images), 1 table. Accepted for publicaton in MNRA

Fast stable direct fitting and smoothness selection for Generalized Additive Models

Existing computationally efficient methods for penalized likelihood GAM fitting employ iterative smoothness selection on working linear models (or working mixed models). Such schemes fail to converge for a non-negligible proportion of models, with failure being particularly frequent in the presence of concurvity. If smoothness selection is performed by optimizing `whole model' criteria these problems disappear, but until now attempts to do this have employed finite difference based optimization schemes which are computationally inefficient, and can suffer from false convergence. This paper develops the first computationally efficient method for direct GAM smoothness selection. It is highly stable, but by careful structuring achieves a computational efficiency that leads, in simulations, to lower mean computation times than the schemes based on working-model smoothness selection. The method also offers a reliable way of fitting generalized additive mixed models

Study the build-up, initiation and acceleration of 2008 April 26 coronal mass ejection observed by STEREO

In this paper, we analyze the full evolution, from a few days prior to the eruption to the initiation, and the final acceleration and propagation, of the CME that occurred on 2008 April 26 using the unprecedented high cadence and multi-wavelength observations by STEREO. There existed frequent filament activities and EUV jets prior to the CME eruption for a few days. These activities were probably caused by the magnetic reconnection in the lower atmosphere driven by photospheric convergence motions, which were evident in the sequence of magnetogram images from MDI (Michelson Doppler Imager) onboard SOHO. The slow low-layer magnetic reconnection may be responsible for the storage of magnetic free energy in the corona and the formation of a sigmoidal core field or a flux rope leading to the eventual eruption. The occurrence of EUV brightenings in the sigmoidal core field prior to the rise of the flux rope implies that the eruption was triggered by the inner tether-cutting reconnection, but not the external breakout reconnection. During the period of impulsive acceleration, the time profile of the CME acceleration in the inner corona is found to be consistent with the time profile of the reconnection electric field inferred from the footpoint separation and the RHESSI 15-25 keV HXR flux curve of the associated flare. The full evolution of this CME can be described in four distinct phases: the build-up phase, initiation phase, main acceleration phase, and propagation phase. The physical properties and the transition between these phases are discussed, in an attempt to provide a global picture of CME dynamic evolution.Comment: 28 pages, 8 figures, accepted for publication in Ap

On the making and taking of professionalism in the further education workplace

This paper examines the changing nature of professional practice in English further education. At a time when neo-liberal reform has significantly impacted on this under-researched and over-market-tested sector, little is known about who its practitioners are and how they construct meaning in their work. Sociological interest in the field has tended to focus on further education practitioners as either the subjects of market and managerial reform or as creative agents operating within the contradictions of audit and inspection cultures. In challenging such dualism, which is reflective of wider sociological thinking, the paper examines the ways in which agency and structure combine to produce a more transformative conception of the further education professional. The approach contrasts with a prevailing policy discourse that seeks to re-professionalise and modernise further education practice without interrogating either the terms of its professionalism or the neo-liberal practices in which it resides

Modeling the System Parameters of 2M1533+3759: A New Longer-Period Low-Mass Eclipsing sdB+dM Binary

We present new photometric and spectroscopic observations for 2M 1533+3759 (= NSVS 07826147). It has an orbital period of 0.16177042 day, significantly longer than the 2.3--3.0 hour periods of the other known eclipsing sdB+dM systems. Spectroscopic analysis of the hot primary yields Teff = 29230 +/- 125 K, log g = 5.58 +/- 0.03 and log N(He)/N(H) = -2.37 +/- 0.05. The sdB velocity amplitude is K1 = 71.1 +/- 1.0 km/s. The only detectable light contribution from the secondary is due to the surprisingly strong reflection effect. Light curve modeling produced several solutions corresponding to different values of the system mass ratio, q(M2/M1), but only one is consistent with a core helium burning star, q=0.301. The orbital inclination is 86.6 degree. The sdB primary mass is M1 = 0.376 +/- 0.055 Msun and its radius is R1 = 0.166 +/- 0.007 Rsun. 2M1533+3759 joins PG0911+456 (and possibly also HS2333+3927) in having an unusually low mass for an sdB star. SdB stars with masses significantly lower than the canonical value of 0.48 Msun, down to as low as 0.30 Msun, were theoretically predicted by Han et al. (2002, 2003), but observational evidence has only recently begun to confirm the existence of such stars. The existence of core helium burning stars with masses lower than 0.40--0.43 Msun implies that at least some sdB progenitors have initial main sequence masses of 1.8--2.0 Msun or more, i.e. they are at least main sequence A stars. The secondary is a main sequence M5 star.Comment: 47 pages, 7 figure