143 research outputs found
A Scheme to Numerically Evolve Data for the Conformal Einstein Equation
This is the second paper in a series describing a numerical implementation of
the conformal Einstein equation. This paper deals with the technical details of
the numerical code used to perform numerical time evolutions from a "minimal"
set of data.
We outline the numerical construction of a complete set of data for our
equations from a minimal set of data. The second and the fourth order
discretisations, which are used for the construction of the complete data set
and for the numerical integration of the time evolution equations, are
described and their efficiencies are compared. By using the fourth order scheme
we reduce our computer resource requirements --- with respect to memory as well
as computation time --- by at least two orders of magnitude as compared to the
second order scheme.Comment: 20 pages, 12 figure
Chain governance, sector policies and economic sustainability in cocoa; A comparative analysis of Ghana, CĂŽte d'Ivoire, and Ecuador
Characteristic Evolution and Matching
I review the development of numerical evolution codes for general relativity
based upon the characteristic initial value problem. Progress in characteristic
evolution is traced from the early stage of 1D feasibility studies to 2D
axisymmetric codes that accurately simulate the oscillations and gravitational
collapse of relativistic stars and to current 3D codes that provide pieces of a
binary black hole spacetime. Cauchy codes have now been successful at
simulating all aspects of the binary black hole problem inside an artificially
constructed outer boundary. A prime application of characteristic evolution is
to extend such simulations to null infinity where the waveform from the binary
inspiral and merger can be unambiguously computed. This has now been
accomplished by Cauchy-characteristic extraction, where data for the
characteristic evolution is supplied by Cauchy data on an extraction worldtube
inside the artificial outer boundary. The ultimate application of
characteristic evolution is to eliminate the role of this outer boundary by
constructing a global solution via Cauchy-characteristic matching. Progress in
this direction is discussed.Comment: New version to appear in Living Reviews 2012. arXiv admin note:
updated version of arXiv:gr-qc/050809
Utilising biological geotextiles: Introduction to the BORASSUS project and global perspectives
Field and laboratory studies indicate that utilisation of biological geotextiles constructed from palm-leaves and other selected organic materials are an effective, sustainable and economically viable soil conservation technique. The three-year plus (1 July 2005â28 February 2009) EU-funded BORASSUS Project (contract no. INCO-CT-2005-510745) evaluated the long-term effectiveness of biological geotextiles in controlling soil erosion and assessing their sustainability and economic viability. These studies progressed in ten countries, both in the âindustrial northâ (in Europe) and in the âdeveloping southâ (Africa, South America and South East Asia). The studied countries in the âdeveloping southâ included Brazil, China, The Gambia, South Africa, Thailand and Vietnam. The âindustrial northâ countries included Belgium, Hungary, Lithuania and the UK. The main findings of these studies are summarised in this paper and thematic information is presented in the other four papers in this Special Issue. Biological geotextiles offer potentially novel bioengineering solutions to environmental problems, including technologies for soil conservation, sustainable plant production and use of indigenous plants, improved ecosystem management by decreasing deforestation, improving agroforestry and cost-effective biogeotextile applications in diverse environments. Biogeotextiles may provide socio-economic platforms for sustainable development and the benefits for developing countries may include poverty alleviation, engagement of local people as stakeholders, employment for disadvantaged groups, small and medium enterprise (SME) development, earning hard currency, environmental education and local community involvement in land reclamation and environmental education programmes. These benefits are achieved through: (i) promotion of sustainable and environmentally friendly palm-agriculture to discourage deforestation, promoting both reforestation and agroforestry; (ii) construction of biogeotextiles enabling development of a rural labour-intensive industry, particularly encouraging employment of socially disadvantaged groups and (iii) export of biogeotextiles to industrialised countries could earn hard currency for developing economies, based on the principles of fair trade. Research and development activities of the BORASSUS Project have improved our knowledge on the effect of biogeotextile mats on the micro- and macro-soil environments and at larger scales through controlled laboratory and field experiments in diverse environments
Designing tree-structured organizations for computational agents
We describe a framework for defining the space of organization designs for computational agents, use our framework for analyzing the expected performance of a class of organizations, and describe how our analyses can be applied to predict performance for a distributed information gathering task. Our analysis specifically addresses the impact of the span of control (branching factor) in tree-structured hierarchical organizations on the response time of such organizations. We show quantitatively how the overall task size and granularity influence the design of the span of control for the organization, and that within the class of organizations considered the apropriate span of control is confined to a relatively narrow range. The performance predicted by our overall model correlates with the actual performance of a distributed organization for computer network monitoring. Consequently, we argue that our framework can support aspects of organizational self-design for computational agents, and might supply insights into the design of human organizations as well.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44720/1/10588_2004_Article_BF00127275.pd
Complete genome sequence of methicillin-sensitive Staphylococcus aureus containing a heterogeneic staphylococcal cassette chromosome element
Staphylococcus aureus is a common human bacterium that sometimes becomes pathogenic, causing serious infections. A key feature of S. aureus is its ability to acquire resistance to antibiotics. The presence of the staphylococcal cassette chromosome (SCC) element in serotypes of S. aureus has been confirmed using multiplex PCR assays. The SCC element is the only vector known to carry the mecA gene, which encodes methicillin resistance in S. aureus infections. Here, we report the genome sequence of a novel methicillin-sensitive S. aureus (MSSA) strain: SCC-like MSSA463. This strain was originally erroneously serotyped as methicillin-resistant S. aureus in a clinical laboratory using multiplex PCR methods. We sequenced the genome of SCC-like MSSA463 using pyrosequencing techniques and compared it with known genome sequences of other S. aureus isolates. An open reading frame (CZ049; AB037671) was identified downstream of attL and attR inverted repeat sequences. Our results suggest that a lateral gene transfer occurred between S. aureus and other organisms, partially changing S. aureus infectivity. We propose that attL and attR inverted repeats in S. aureus serve as frequent insertion sites for exogenous genes.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000316747000011&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701BiologySCI(E)PubMed0ARTICLE3268-2745
Characteristic Evolution and Matching
I review the development of numerical evolution codes for general relativity
based upon the characteristic initial value problem. Progress is traced from
the early stage of 1D feasibility studies to 2D axisymmetric codes that
accurately simulate the oscillations and gravitational collapse of relativistic
stars and to current 3D codes that provide pieces of a binary black spacetime.
A prime application of characteristic evolution is to compute waveforms via
Cauchy-characteristic matching, which is also reviewed.Comment: Published version http://www.livingreviews.org/lrr-2005-1
Chain Governance, Sector Policies and Economic Sustainability in Cocoa: A Comparative Analysis of Ghana, CĂŽte DâIvoire, and Ecuador
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