431 research outputs found
Activated vortex lattice transition in a superconductor with combined sixfold and twelvefold anisotropic interactions
Numerical simulations are used to examine the transition dynamics between
metastable and ground state vortex lattice phases in a system with combined
sixfold and twelvefold contributions to the vortex-vortex interactions. The
system is initially annealed using a twelvefold anisotropy, yielding domains of
two different orientations and separated by grain boundaries. The vortex-vortex
interaction is then suddenly changed to a sixfold anisotropy, rendering the
twelvefold state metastable. Applying a drive that mimics an oscillating
magnetic field causes the metastable state to decay, indicated by the structure
factor that evolves from twelve to six peaks. The results fit the behavior seen
in recent small-angle neutron scattering studies of the vortex lattice in MgB2.
At higher drive amplitudes, the decay exhibits a two step process in which the
initial fast decrease is followed by a slower regime where avalanches or bursts
are correlated with dislocation annihilation events. The results are compared
to other types of metastable systems with quenched disorder that decay under a
periodic external drive.Comment: Accepted for publication, New J. Phy
Comparison of nucleic acid extraction platforms for detection of select biothreat agents for use in clinical resource limited settings
High-quality nucleic acids are critical for optimal PCR-based diagnostics and pathogen detection. Rapid sample processing time is important for the earliest administration of therapeutic and containment measures, especially in the case of biothreat agents. In this context, we compared the Fujifilm QuickGene-Mini80 to Qiagen\u27s QIAamp Mini Purification kits for extraction of DNA and RNA for potential use in austere settings. Qiagen (QIAamp) column-based extraction is the currently recommended purification platform by United States Army Medical Research Institute for Infectious Diseases for both DNA and RNA extraction. However, this sample processing system requires dedicated laboratory equipment including a centrifuge. In this study, we investigated the QuickGene-Mini80, which does not require centrifugation, as a suitable platform for nucleic acid extraction for use in resource-limited locations. Quality of the sample extraction was evaluated using pathogen-specific, real-time PCR assays for nucleic acids extracted from viable and γ-irradiated Bacillus anthracis, Yersinia pestis, vaccinia virus, Venezuelan equine encephalitis virus, or B. anthracis spores in buffer or human whole blood. QuickGene-Mini80 and QIAamp performed similarly for DNA extraction regardless of organism viability. It was noteworthy that γ-irradiation did not have a significant impact on real-time PCR for organism detection. Comparison with QIAamp showed a less than adequate performance of the Fujifilm instrument for RNA extraction. However, QuickGene-Mini80 remains a viable alternative to QIAamp for DNA extraction for use in remote settings due to extraction quality, time efficiency, reduced instrument requirements, and ease of use
The Politics of Service Delivery Reform
This article identifies the leaders, the supporters and the resisters of public service reform. It adopts a principal–agent framework, comparing reality with an ‘ideal’ situation in which citizens are the principals over political policy-makers as their agents, and policy-makers are the principals over public service officials as their agents. Reform in most developing countries is complicated by an additional set of external actors — international financial institutions and donors. In practice, international agencies and core government officials usually act as the ‘principals’ in the determination of reforms. The analysis identifies the interests involved in reform, indicating how the balance between them is affected by institutional and sectoral factors. Organizational reforms, particularly in the social sectors, present greater difficulties than first generation economic policy reforms
A Cellular Automata Model for Citrus Variagated Chlorosis
A cellular automata model is proposed to analyze the progress of Citrus
Variegated Chlorosis epidemics in S\~ao Paulo oranges plantation. In this model
epidemiological and environmental features, such as motility of sharpshooter
vectors which perform L\'evy flights, hydric and nutritional level of plant
stress and seasonal climatic effects, are included. The observed epidemics data
were quantitatively reproduced by the proposed model varying the parameters
controlling vectors motility, plant stress and initial population of diseased
plants.Comment: 10 pages, 10 figures, Scheduled tentatively for the issue of: 01Nov0
Oxysterol Binding Protein-dependent Activation of Sphingomyelin Synthesis in the Golgi Apparatus Requires Phosphatidylinositol 4-Kinase IIα
The study identifies a sterol- and oxysterol binding protein (OSBP)-regulated phosphatidylinositol 4-kinase that regulates ceramide transport protein (CERT) activity and sphingomyelin (SM) synthesis. RNA interference silencing experiments identify PI4KIIα; as the mediator of Golgi recruitment of CERT, providing a potential mechanism for coordinating assembly of SM and cholesterol in the Golgi or more distal compartments
Ecological Invasion, Roughened Fronts, and a Competitor's Extreme Advance: Integrating Stochastic Spatial-Growth Models
Both community ecology and conservation biology seek further understanding of
factors governing the advance of an invasive species. We model biological
invasion as an individual-based, stochastic process on a two-dimensional
landscape. An ecologically superior invader and a resident species compete for
space preemptively. Our general model includes the basic contact process and a
variant of the Eden model as special cases. We employ the concept of a
"roughened" front to quantify effects of discreteness and stochasticity on
invasion; we emphasize the probability distribution of the front-runner's
relative position. That is, we analyze the location of the most advanced
invader as the extreme deviation about the front's mean position. We find that
a class of models with different assumptions about neighborhood interactions
exhibit universal characteristics. That is, key features of the invasion
dynamics span a class of models, independently of locally detailed demographic
rules. Our results integrate theories of invasive spatial growth and generate
novel hypotheses linking habitat or landscape size (length of the invading
front) to invasion velocity, and to the relative position of the most advanced
invader.Comment: The original publication is available at
www.springerlink.com/content/8528v8563r7u2742
Sustainable development and African local government: can electronic training help build capacities?
A recent study carried out by European and African organizations into the potential for electronic distance training (EDT) on sustainability in African local governments concluded that EDT was both 'useful and feasible'. This article reflects on some of the theoretical and practical implications of that study. It focuses on the connection between learning and sustainability and how EDT programmes might be designed and promoted. The paper argues that, while resource issues and poor access to Information and Communication Technologies (ICTs) create considerable constraints and point to the need for policies to improve access, in general the most important factors for successful capacity building relate to the design of learning programmes that take account of the work contexts and skill and capability requirements of those targeted as learners. 'Useful' and 'feasible' depend on (i) how work-based and work-related learning processes are understood and (ii) the conditions to promote learning within African local government.
Keywords: Africa; Electronic distance training; Local government; Sustainability; Workplace learnin
Operationalising a model framework for consumer and community participation in health and medical research
The Consumers' Health Forum of Australia and the National Health and Medical Research Council has recently developed a Model Framework for Consumer and Community Participation in Health and Medical Research in order to better align health and medical research with community need, and improve the impact of research. Model frameworks may have little impact on what goes on in practice unless relevant organisations actively make use of them. Philanthropic and government bodies have reported involving consumers in more meaningful or collaborative ways of late. This paper describes how a large charity organisation, which funds a significant proportion of Australian cancer research, operationalised the model framework using a unique approach demonstrating that it is both possible and reasonable for research to be considerate of public values
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