A New Agro-Meteorological Simulation Model for Predicting Daily Grass Growth Rates Across Ireland

Grass growth rates and herbage yields depend on weather conditions, soil characteristics and grassland management and differ from year to year and from site to site. In the past, grass growth has been predicted using both mechanistic and statistical models. The accuracy of mechanistic models is commonly insufficient for practical application, while statistical models generally apply to one test site only (e.g. Han et al., 2003). In this paper a semi-empirical grass growth model is presented which is numerically accurate, but which can be applied to contrasting sites across Ireland at the same time

Polarimetric Evidence of Non-Spherical Winds

Polarization observations yield otherwise unobtainable information about the geometrical structure of unresolved objects. In this talk we review the evidences for non-spherically symmetric structures around Luminous Hot Stars from polarimetry and what we can learn with this technique. Polarimetry has added a new dimension to the study of the envelopes of Luminous Blue Variables, Wolf-Rayet stars and B[e] stars, all of which are discussed in some detail.Comment: 8 pages, 2 encapsulated Postscript figures, uses lamuphys.sty. Invited review to appear in IAU Coll. 169, Variable and Non-Spherical Stellar Winds in Luminous Hot Stars, eds. B. Wolf, A.Fullerton and O. Stahl (Springer

The Effect of Grassland Management on Bovine Nitrogen Efficiency

Nitrogen (N) losses through grazing bovines are at the heart of the current debate on environment and agriculture. N utilisation of grazing bovines is predominantly determined by the form and amount of energy and protein in their diet, which in Ireland consists mainly of grazed grass. The two main problems of grazed grass with respect to animal N utilisation are 1) the imbalance between total N content and energy content, and 2) the lack of synchronisation between the release of N and carbohydrates in the rumen. It was hypothesised that both the balance and synchronisation of N and energy in herbage could be improved through grassland management. The objective of this study was to study the effect of grassland management on herbage carbohydrate and protein fractionation

Bosons in Disordered Optical Potentials

In this work we systematically investigate the condensate properties, superfluid properties and quantum phase transitions in interacting Bose gases trapped in disordered optical potentials. We numerically solve the Bose-Hubbard Hamiltonian exactly for different: (a) types of disorder, (b) disorder strengths, and (c) interatomic interactions. The three types of disorder studied are: quasiperiodic disorder, uniform random disorder and random speckle-type disorder. We find that the Bose glass, as identified by Fisher et al [Phys. Rev. B {\bf 40}, 546 (1989)], contains a normal condensate component and we show how the three different factors listed above affect it.Comment: 4 pages, 4 figures (low res) v2 Title,Abstract,Introduction: changes; Figure 3: Add label to axi

The Oldest Stars of the Extremely Metal-Poor Local Group Dwarf Irregular Galaxy Leo A

We present deep Hubble Space Telescope single-star photometry of Leo A in B, V, and I. Our new field of view is offset from the centrally located field observed by Tolstoy et al. (1998) in order to expose the halo population of this galaxy. We report the detection of metal-poor red horizontal branch stars, which demonstrate that Leo A is not a young galaxy. In fact, Leo A is as least as old as metal-poor Galactic Globular Clusters which exhibit red horizontal branches, and are considered to have a minimum age of about 9 Gyr. We discuss the distance to Leo A, and perform an extensive comparison of the data with stellar isochrones. For a distance modulus of 24.5, the data are better than 50% complete down to absolute magnitudes of 2 or more. We can easily identify stars with metallicities between 0.0001 and 0.0004, and ages between about 5 and 10 Gyr, in their post-main-sequence phases, but lack the detection of main-sequence turnoffs which would provide unambiguous proof of ancient (>10 Gyr) stellar generations. Blue horizontal branch stars are above the detection limits, but difficult to distinguish from young stars with similar colors and magnitudes. Synthetic color-magnitude diagrams show it is possible to populate the blue horizontal branch in the halo of Leo A. The models also suggest ~50% of the total astrated mass in our pointing to be attributed to an ancient (>10 Gyr) stellar population. We conclude that Leo A started to form stars at least about 9 Gyr ago. Leo A exhibits an extremely low oxygen abundance, of only 3% of Solar, in its ionized interstellar medium. The existence of old stars in this very oxygen-deficient galaxy illustrates that a low oxygen abundance does not preclude a history of early star formation.Comment: 44 pages, 18 figures, accepted for publication in the August 2002 issue of AJ. High resolution figures is available at http://www.astro.spbu.ru/staff/dio/preprints.htm

A multi-method approach for the integrative assessment of soil functions: Application on a coastal mountainous site of the Philippines

The projected increase of the world\u27s population and the sustainability challenges the agricultural sector is facing, call for the enhancement of multi-functionality in agriculture in order to simultaneously provide food while meeting environmental targets. Here, we use the Functional Land Management (FLM) framework to assess the supply of and the demand for soil functions to inform agri-environmental policy for Udalo, a mountainous site in the Philippines. As many emerging communities in developing nations, Udalo is on the cusp of rapid development due to the construction of a major road increasing its accessibility and attractiveness for land investment. We assessed the supply of four soil functions in relation to six land-use types and four slope categories. The function “productivity” was assessed by interviews with 128 farmers, “habitat for biodiversity” by a vegetation survey, and “soil conservation” and “water conservation” via a literature review. The demand for functions was first assessed from the “top-down” policy perspective via interviews and reviews of policy targets, then complemented by integrating the local “bottom-up” demands for functions. These were assessed by applying a Q methodology, providing insights in the prioritisation of functions from the perspective of 22 local actors. Maps of supply and demands were generated for each function: supply maps by overlaying land use and slope category, top-down demand maps from administrative zoning/land-use plans, and bottom-up demand maps from local actors designation of geomorphological areas. Our results revealed contrasting demands for functions, as well as a heterogeneous spatial distribution of supply and demands. Discrepancies emerged (i) between supply and demand, (ii) between bottom-up (local) demands and the top-down (policy driven) demand, and (iii) among local actors perspectives. Our study indicates that discrepancies are not necessarily conflicting, but can uncover pathways for defining compromises, representing attainable policy entry points. Not one single development model can meet the needs of every stakeholder; however, a combination of land uses and management strategies can meet divergent interests and allow for optimisation of functions. This integrative approach of FLM provides a socially embedded biophysical analysis and is a valuable tool for the design of customized land-use and agri-environmental policies

A Search for Sigma^0_5, N^0_5 and Theta^++ Pentaquark States

A high-resolution (sigma_instr. = 1.5 MeV) search for narrow states (Gamma < 10 MeV) with masses of M_x approx 1500-1850 MeV in ep -> e'K^+ X, e'K^- X and e' pi^+ X electroproduction at small angles and low Q^2 was performed. These states would be candidate partner states of the reported Theta^+(1540) pentaquark. No statistically significant signal was observed in any of the channels at 90% C.L. Upper limits on forward production were determined to be between 0.7% and 4.2% of the Lambda(1520) production cross section, depending on the channel and the assumed mass and width of the state.Comment: 5 pages, 5 figures, to appear in Phys. Rev. C, update with responses to referee suggestion