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The design of sustainable intensive livestock production systems for developing countries must be judged according to their likely impact on economic, ecological, ethological and sociological issues. Economic issues to be satisfied include international competitivity in price of finished products which requires maximizing comparative advantages of available natural resources. Ecological sustainability requires that the production system will result in (i) reduced emissions of the principal greenhouse gases carbon dioxide and methane; (ii) reduced contamination of soil and water resources; (iii) an effective control of soil erosion; and (iv) self sufficiency in on-farm production of energy from renewable resources. Ethological concerns relate to potential effects of production systems on animal welfare and the safety and consumer acceptability (wholesomeness) of foods produced in such systems. Sociological acceptability requires that employment opportunities are increased, especially for women, and that the production system encourages self-reliance with minimum dependence on outside inputs.
The basic technology, designed and adapted by Convenio Interinstitucional para la Producción Pecuaria en el Valle del Rio Cauca (CIPAV) and cooperating local farmers in the Cauca Valley of Colombia, uses sugar cane, multipurpose trees and water plants as sources of biomass to provide food for a range of livestock species and fuel for the farm and the family. The chosen crops have a proven high capacity to fix atmospheric carbon dioxide and nitrogen into biomass, which is a permanent carbon reservoir (1 ha planted in sugar cane and trees is a sink for some 80 t carbon dioxide), and also a source of substrate for food and fuel. Sugar cane and trees help prevent erosion, maintain soil fertility, have well developed systems of biological pest control, require minimum synthetic chemical inputs and are easily separated into high and low fibre fractions as required for the different end uses of food for monogastric and ruminant animals and fuel.
The preferred animal species are pigs and ducks which adapt readily to the ‘non-conventional’ high-moisture food resources (mainly cane juice, tree leaves and water plants) and have a high meat : methane production ratio. They are complemented by African sheep, dual purpose (Holsteinzebu) cattle and buffaloes, managed as triple purpose animals (draught, milk and meat) and deriving most of their food from the more nutritive parts of the fibrous crop residues. All the livestock are managed in partial or total confinement to minimize environmental damage and to maximize nutrient recycling to the crops.
Fuel for the family is derived from the biodigestor which uses as substrate the excreta from the pigs; and from the sugar cane bagasse. Earthworms upgrade the fertilizer value of the excreta from the ruminant animals and produce part of the protein for the ducks.
The CIPAV model is flexible as witnessed by the increasing acceptance of many of the elements in the model by both resource-poor and entrepreneurial farmers. The biomass concept, on which the CIPAV model is based, can also be scaled up to the level of agro-industry (the biomass refinery) offering renewable alternatives to present fossil-fuel-based technologies for chemical and energy needs.
In-spiraling supermassive black holes should emit gravitational waves, which would produce characteristic distortions in the time of arrival residuals from millisecond pulsars. Multiple national and regional consortia have constructed pulsar timing arrays by precise timing of different sets of millisecond pulsars. An essential aspect of precision timing is the transfer of the times of arrival to a (quasi-)inertial frame, conventionally the solar system barycenter. The barycenter is determined from the knowledge of the planetary masses and orbits, which has been refined over the past 50 years by multiple spacecraft. Within the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), uncertainties on the solar system barycenter are emerging as an important element of the NANOGrav noise budget. We describe what is known about the solar system barycenter, touch upon how uncertainties in it affect gravitational wave studies with pulsar timing arrays, and consider future trends in spacecraft navigation.
PSR J0337+1715 is a millisecond radio pulsar in a hierarchical stellar triple system with two white dwarfs. This system is a unique and excellent laboratory in which to test the strong equivalence principle (SEP) of general relativity. An initial SEP-violation test was performed using direct 3-body numerical integration of the orbit in order to model the more than 25000 pulse times of arrival (TOAs) from three radio telescopes: Arecibo, Green Bank and Westerbork. In this work I present our efforts to quantify the effects of systematics in the TOAs and timing residuals, which limit the precision of an SEP test. In particular, we apply Fourier-based techniques to the timing residuals in order to isolate the effects of systematics that can masquerade as an SEP violation.
The Square Kilometre Array will be an amazing instrument for pulsar astronomy. While the full SKA will be sensitive enough to detect all pulsars in the Galaxy visible from Earth, already with SKA1, pulsar searches will discover enough pulsars to increase the currently known population by a factor of four, no doubt including a range of amazing unknown sources. Real time processing is needed to deal with the 60 PB of pulsar search data collected per day, using a signal processing pipeline required to perform more than 10 POps. Here we present the suggested design of the pulsar search engine for the SKA and discuss challenges and solutions to the pulsar search venture.
Phased Array Feed (PAF) technology is the next major advancement in radio astronomy in terms of combining high sensitivity and large field of view. The Focal L-band Array for the Green Bank Telescope (FLAG) is one of the most sensitive PAFs developed so far. It consists of 19 dual-polarization elements mounted on a prime focus dewar resulting in seven beams on the sky. Its unprecedented system temperature of ~17 K will lead to a 3 fold increase in pulsar survey speeds as compared to contemporary single pixel feeds. Early science observations were conducted in a recently concluded commissioning phase of the FLAG where we clearly demonstrated its science capabilities. We observed a selection of normal and millisecond pulsars and detected giant pulses from PSR B1937+21.
The majority of fast radio bursts (FRBs) are poorly localised, hindering their potential scientific yield as galactic, intergalactic, and cosmological probes. LOFT-e, a digital backend for the U.K.’s e-MERLIN seven-telescope interferometer will provide commensal search and real-time detection of FRBs, taking full advantage of its field of view (FoV), sensitivity, and observation time. Upon burst detection, LOFT-e will store raw data offline, enabling the sub-arcsecond localisation provided by e-MERLIN and expanding the pool of localised FRBs. The high-time resolution backend will additionally introduce pulsar observing capabilities to e-MERLIN.
The millisecond pulsar PSR J0337+1715 is in a mildly relativistic hierarchical triple system with two white dwarfs. This offers the possibility of testing the universality of free fall: does the neutron star fall with the same acceleration as the inner white dwarf in the gravity of the outer white dwarf? We have carried out an intensive pulsar timing campaign, yielding some 27000 pulse time-of-arrival (TOA) measurements with a median uncertainty of 1.2 μs. Here we describe our analysis procedure and timing model.
Phased VLA observations of the Galactic center magnetar J1745-2900 over 8-12 GHz reveal rich single pulse behavior. The average profile is comprised of several distinct components and is fairly stable over day timescales and GHz frequencies. The average profile is dominated by the jitter of relatively narrow pulses. The pulses in each of the four profile components are uncorrelated in phase and amplitude, although the occurrence of pulse components 1 and 2 appear to be correlated. Using a collection of the brightest individual pulses, we verify that the index of the dispersion law is consistent with the expected cold plasma value of 2. The scattering time is weakly constrained, but consistent with previous measurements, while the dispersion measure DM = 1763+3−10 pc cm−3 is lower than previous measurements, which could be a result of time variability in the line-of-sight column density or changing pulse profile shape over time or frequency.
An evolution of the low-frequency pulse profile of PSR B2217+47 is observed during a six-year observing campaign with the LOFAR telescope at 150 MHz. The evolution is manifested as a new component in the profile trailing the main peak. The leading part of the profile, including a newly-observed weak component, is steady during the campaign. The transient component is not visible in simultaneous observations at 1500 MHz using the Lovell telescope, implying a chromatic effect. A variation in the dispersion measure of the source is detected in the same timespan. Precession of the pulsar and changes in the magnetosphere are investigated to explain the profile evolution. However, the listed properties favour a model based on turbulence in the interstellar medium (ISM). This interpretation is confirmed by a strong correlation between the intensity of the transient component and main peak in single pulses. Since PSR B2217+47 is the fourth brightest pulsar visible to LOFAR, we speculate that ISM-induced pulse profile evolution might be relatively common but subtle and that SKA-Low will detect many similar examples. In this scenario, similar studies of pulse profile evolution could be used in parallel with scintillation arcs to characterize the properties of the ISM.
In August 2017 a new radio telescope, the Ghana Radio Astronomy Observatory (GRAO), was officially inaugurated at Kuntunse, Ghana. The GRAO is a former satellite Earth station and now the first operational station in the African VLBI Network (AVN). The Jodrell Bank Centre for Astrophysics (JBCA), supported by the UK’s STFC/Newton Fund, has developed a new pulsar timing system (Hebe) for the GRAO. We present some aspects of the design of Hebe and an outline of the first pulsar detection at GRAO.
The class of radio transients called Fast Radio Bursts (FRBs) encompasses enigmatic single pulses, each unique in its own way, hindering a consensus for their origin. The key to demystifying FRBs lies in discovering many of them in order to identity commonalities – and in real time, in order to find potential counterparts at other wavelengths. The recently upgraded UTMOST in Australia, is undergoing a backend transformation to rise as a fast transient detection machine. The first interferometric detections of FRBs with UTMOST, place their origin beyond the near-field region of the telescope thus ruling out local sources of interference as a possible origin. We have localised these bursts to much better than the ones discovered at the Parkes radio telescope and have plans to upgrade UTMOST to be capable of much better localisation still.
Preston et al (1976) and Burke (1982, these proceedings) have long extolled the virtues of launching a radio telescope into space to increase VLBI baseline lengths and thus angular resolution, and to provide a much enhanced image formation capability. The scientific motivation for this has been covered in a number of memoranda referenced by Burke in these proceedings, and by Anderson et al (1982). Efforts to mobilise western astronomical support for space VLBI met with success in late 1982 at a meeting of US and European radio astronomers in Toulouse, France, at which a decision was taken to propose a joint mission to ESA and NASA. Shortly thereafter, a formal proposal was made to ESA (Anderson et al 1982) for a free flying satellite in an elliptical orbit out to 15000 km from the Earth, designed to observe in concert with the major ground-based VLBI networks and arrays. The mission, dubbed QUASAT, was received favourably in both ESA and NASA, with the result that formal Assessment Studies are scheduled to begin in both agencies in October 1983.
In studies of extragalactic radio sources with multiple compact components the determination of which components, if any, are stationary and which moving is of importance. In order to learn about the radio properties of the individual components it is also relevant to be able to register maps made at several wavelengths. Both tasks are usually not possible with VLBI because of the irrecoverable corruption of the fringe phase introduced by the propagation medium and the instrumentation. However, when two or more compact radio sources are separated by only a small angle from each other difference techniques can be used to help tackle both questions.
VLBI observations at 2.3 GHz of SN1987A on 28 February 1987 yielded no fringes, implying, for an optically thin shell, a lower bound on the (outer) diameter of 1.9 mas. From the comparison of the VLBI and optical results, we infer that the radiosphere of SN1987A was either about equal to, or larger than, the photosphere of the supernova five days after the explosion.
A global array of 20 radio observatories was used to measure the three-dimensional position and velocity of the two meteorological balloons that were injected into the equatorial region of the Venus atmosphere by the VEGA spacecraft.