17,593 research outputs found
Translational Genomics for Alfalfa Varietal Improvement
Key points Medicago truncatula is a model legume with available mapping, genome, and RNA, protein and metabolite profiling databases and genetically diverse populations. Genomics resources developed for M. truncatula have application in the study and improvement of alfalfa making it an excellent model for this forage legume
Using a Combination of Micro-Computed Tomography, CAD and 3D Printing Techniques to Reconstruct Incomplete 19th-Century Cantonese Chess Pieces
Secondary literacy across the curriculum: Challenges and possibilities
This paper discusses the challenges and possibilities attendant upon successfully implementing literacy across the curriculum initiatives – or ‘school language policies’ as they have come to be known - particularly at the secondary or high school level. It provides a theoretical background to these issues, exploring previous academic discussions of school language policies, and highlights key areas of concern as well as opportunity with respect to school implementation of such policies. As such, it provides a necessary conceptual background to the subsequent papers in this special issue, which focus upon the Secondary Schools’ Literacy Initiative (SSLI) – a New Zealand funded programme that aims to establish cross-curricular language and literacy policies in secondary schools
Eigenvalue Separation in Some Random Matrix Models
The eigenvalue density for members of the Gaussian orthogonal and unitary
ensembles follows the Wigner semi-circle law. If the Gaussian entries are all
shifted by a constant amount c/Sqrt(2N), where N is the size of the matrix, in
the large N limit a single eigenvalue will separate from the support of the
Wigner semi-circle provided c > 1. In this study, using an asymptotic analysis
of the secular equation for the eigenvalue condition, we compare this effect to
analogous effects occurring in general variance Wishart matrices and matrices
from the shifted mean chiral ensemble. We undertake an analogous comparative
study of eigenvalue separation properties when the size of the matrices are
fixed and c goes to infinity, and higher rank analogues of this setting. This
is done using exact expressions for eigenvalue probability densities in terms
of generalized hypergeometric functions, and using the interpretation of the
latter as a Green function in the Dyson Brownian motion model. For the shifted
mean Gaussian unitary ensemble and its analogues an alternative approach is to
use exact expressions for the correlation functions in terms of classical
orthogonal polynomials and associated multiple generalizations. By using these
exact expressions to compute and plot the eigenvalue density, illustrations of
the various eigenvalue separation effects are obtained.Comment: 25 pages, 9 figures include
An Economic Comparison Of Year Round vs Conventional Grazing Systems In Iowa
Year round grazing systems that utilize stockpiled forage and/or crop residue are often promoted as a way for Northern and Western cow-calf producers to reduce winter feeding costs and improve overall profitability. This study compared the profitability of a conventional spring calving/summer grazing- winter drylot herd to a year round system that utilized both spring- and fall-calving herds with weaned calves retained as stockers. Forage supplies in the year round system were derived from stockpiled forage and corn crop residues. We developed a model that randomly generated production values with parameters based on the results of a 3-year study conducted at the Iowa State University McNay Research and Demonstration farm near Chariton, Iowa. The simulated production values were combined with livestock and forage prices prevailing from 1993-2001 to estimate income per head generated by each system. Average income over the nine- year period was equal. However, the year round system was economically superior in 3 years, equivalent in 1 year, and inferior in 5 years.
Overcoming the barriers to implementing urban road user charging schemes
Urban road user charging offers the potential to achieve significant improvements in urban transport, but is notoriously difficult to implement. Cities need guidance on the range of factors to be considered in planning and implementing such schemes. This paper summarises the results of a 3 year programme which has collated evidence on the issues of most concern to cities. A state of the art report has provided evidence on 14 themes, ranging from objectives and design to implementation and evaluation. A set of 16 case studies has reviewed experience in design and implementation across Europe. The paper summarises their findings, provides references to more detailed information, presents the resulting policy recommendations to European, national and local government, and outlines the areas in which further research is needed
Emergence of diversity in a model ecosystem
The biological requirements for an ecosystem to develop and maintain species
diversity are in general unknown. Here we consider a model ecosystem of sessile
and mutually excluding organisms competing for space [Mathiesen et al. Phys.
Rev. Lett. 107, 188101 (2011)]. The competition is controlled by an interaction
network with fixed links chosen by a Bernoulli process. New species are
introduced in the system at a predefined rate. In the limit of small
introduction rates, the system becomes bistable and can undergo a phase
transition from a state of low diversity to high diversity. We suggest that
patches of isolated meta-populations formed by the collapse of cyclic relations
are essential for the transition to the state of high diversity.Comment: 7 pages, 6 figures. Accepted for publication in PRE. Typos corrected,
Fig.3A and Fig.6 update
Complementarity and diversity in a soluble model ecosystem
Complementarity among species with different traits is one of the basic
processes affecting biodiversity, defined as the number of species in the
ecosystem. We present here a soluble model ecosystem in which the species are
characterized by binary traits and their pairwise interactions follow a
complementarity principle. Manipulation of the species composition, and so the
study of its effects on the species diversity is achieved through the
introduction of a bias parameter favoring one of the traits. Using statistical
mechanics tools we find explicit expressions for the allowed values of the
equilibrium species concentrations in terms of the control parameters of the
model
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