3,817 research outputs found
Niches, rather than neutrality, structure a grassland pioneer guild
Pioneer species are fast-growing, short-lived gap exploiters. They are prime candidates for neutral dynamics because they contain ecologically similar species whose low adult density is likely to cause widespread recruitment limitation, which slows competitive dynamics. However, many pioneer guilds appear to be differentiated according to seed size. In this paper, we compare predictions from a neutral model of community structure with three niche-based models in which trade-offs involving seed size form the basis of niche differentiation. We test these predictions using sowing experiments with a guild of seven pioneer species from chalk grassland. We find strong evidence for niche structure based on seed size: specifically large-seeded species produce fewer seeds but have a greater chance of establishing on a per-seed basis. Their advantage in establishment arises because there are more microsites suitable for their germination and early establishment and not directly through competition with other seedlings. In fact, seedling densities of all species were equally suppressed by the addition of competitors' seeds. By the adult stage, despite using very high sowing densities, there were no detectable effects of interspecific competition on any species. The lack of interspecific effects indicates that niche differentiation, rather than neutrality, prevails
Coercivity and stability results for an extended Navier-Stokes system
In this article we study a system of equations that is known to {\em extend}
Navier-Stokes dynamics in a well-posed manner to velocity fields that are not
necessarily divergence-free. Our aim is to contribute to an understanding of
the role of divergence and pressure in developing energy estimates capable of
controlling the nonlinear terms. We address questions of global existence and
stability in bounded domains with no-slip boundary conditions. Even in two
space dimensions, global existence is open in general, and remains so,
primarily due to the lack of a self-contained energy estimate. However,
through use of new coercivity estimates for the linear equations, we
establish a number of global existence and stability results, including results
for small divergence and a time-discrete scheme. We also prove global existence
in 2D for any initial data, provided sufficient divergence damping is included.Comment: 29 pages, no figure
What works and for whom: a review of OECD countries' experiences with active labour market policies
Although rather discouraging in general, the evaluation literature indicates some measures that have been successful. Job-search assistance, wage subsidies in the private sector, and labour market training do work for some groups, even if the impacts are not large. Also, the evaluation literature focuses on the impacts of one-off programs. Regular interventions, such as job-search monitoring, intensive interviews, and referrals to vacant jobs, have rarely been evaluated rigorously. Recently, introduced "activation" strategies in some OECD countries do appear to yield significant employment gains for participants. An important element in such strategies is experiments with alternative ways of improving the performance of the public employment service. Activation policies which combine high-quality assistance to find work with pressure on unemployed people to accept job offers can be effective with respect to unemployment duration, but more rapid returns to work sometimes comes at the cost of accepting lower re-employment earnings. Although active policies might give rise to displacement effects in the short run, this need not be case the over the medium run of a few years. Declines in structural employment rates achieved by many OECD countries in the 1990s give some reasons for optimism in this respect.job search; wage subsidies; labour market training
Consolidated List of Requirements
This document is a consolidated catalogue of requirements for the Electronic
Health Care Record (EHCR) and Electronic Health Care Record Architecture
(EHCRA), gleaned largely from work done in the EU Framework III and IV
programmes and CEN, but also including input from other sources including world-wide
standardisation initiatives. The document brings together the relevant work done into a
classified inventory of requirements to inform the on-going standardisation process as
well as act as a guide to future implementation of EHCRA-based systems. It is meant as
a contribution both to understanding of the standard and to the work that is being
considered to improve the standard. Major features include the classification into issues
affecting the Health Care Record, the EHCR, EHCR processing, EHCR interchange and
the sharing of health care information and EHCR systems. The principal information
sources are described briefly. It is offered as documentation that is complementary to the
four documents of the ENV 13606 Parts I-IV produced by CEN Pts 26,27,28,29. The
requirements identified and classified in this deliverable are referenced in other
deliverables
Health informatics education for clinicians and managers - What's holding up progress?
This paper reports outcomes of a national survey of health informatics (HI) education and training carried out in the UK. A questionnaire to elicit details of HI and IT skills teaching was derived from a national consensus document (Learning to Manage Health Information, LtMHI). Forms were sent to all pre-qualification medical and nursing schools and to a stratified sample of postgraduate and post-registration programmes. Three case studies were carried out in acute hospital trusts to gain insight into opportunities for continuing professional development in health informatics and IT. Our evidence suggests that in the UK, health informatics is not yet integrated into the clinical curriculum. Nearly all the pre-qualification courses made some provision for teaching IT skills. Nonetheless, many respondents felt that students did not receive sufficient training. There was considerable variation in the amount of HI teaching provided in the different educational sectors. The case studies suggested very little HI training was provided for clinical staff and take-up of provision was not monitored. A number of factors are holding up progress, the most important being a lack of staff with the knowledge and skills to provide academic leadership. The paper outlines some steps that need to be taken to ensure health informatics is embedded in all clinical curricula. © 2003 Elsevier Ireland Ltd. All rights reserved
Smeared heat-kernel coefficients on the ball and generalized cone
We consider smeared zeta functions and heat-kernel coefficients on the
bounded, generalized cone in arbitrary dimensions. The specific case of a ball
is analysed in detail and used to restrict the form of the heat-kernel
coefficients on smooth manifolds with boundary. Supplemented by conformal
transformation techniques, it is used to provide an effective scheme for the
calculation of the . As an application, the complete coefficient
is given.Comment: 23 pages, JyTe
- …