18,884 research outputs found
Self-consistency of relativistic observables with general relativity in the white dwarf-neutron star binary pulsar PSR J1141-6545
Here we report timing measurements of the relativistic binary pulsar PSR
J1141-6545 that constrain the component masses and demonstrate that the orbital
period derivative \dot Pb = (-4+/-1)x10^-13 is consistent with gravitational
wave emission as described by the general theory of relativity. The mass of the
neutron star and its companion are 1.30+/-0.02 Mo and 0.986+/-0.020 Mo
respectively, suggesting a white dwarf companion, and extending the range of
systems for which general relativity provides a correct description. On
evolutionary grounds, the progenitor mass of PSR J1141-6545 should be near the
minimum for neutron star production. Its mass is two standard deviations below
the mean of the other neutron stars, suggesting a relationship between
progenitor and remnant masses.Comment: 10 pages, 2 figures, revised version to Ap J Letter
An Economic analysis of the potential for precision farming in UK cereal production
The results from alternative spatial nitrogen application studies are analysed in economic terms and compared to the costs of precision farming hardware, software and other services for cereal crops in the UK. At current prices, the benefits of variable rate application of nitrogen exceed the returns from a uniform application by an average of £22 ha−1 The cost of the precision farming systems range from £5 to £18 ha−1 depending upon the system chosen for an area of 250 ha. The benefits outweigh the associated costs for cereal farms in excess of 80 ha for the lowest price system to 200–300 ha for the more sophisticated systems. The scale of benefits obtained depends upon the magnitude of the response to the treatment and the proportion of the field that will respond. To be cost effective, a farmed area of 250 ha of cereals, where 30% of the area will respond to variable treatment, requires an increase in crop yield in the responsive areas of between 0·25 and 1.00 t ha−1 (at £65 t−1) for the basic and most expensive precision farming systems, respectively
Low attentional engagement makes attention network activity susceptible to emotional interference
The aim of this study was to investigate whether emotion-attention interaction depends on attentional engagement. To investigate emotional modulation of attention network activation, we used a functional MRI paradigm consisting of a visuospatial attention task with either frequent (high-engagement) or infrequent (low-engagement) targets and intermittent emotional or neutral distractors. The attention task recruited a bilateral frontoparietal network with no emotional interference on network activation when the attentional engagement was high. In contrast, when the attentional engagement was low, the unpleasant stimuli interfered with the activation of the frontoparietal attention network, especially in the right hemisphere. This study provides novel evidence for low attentional engagement making attention control network activation susceptible to emotional interference. © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins.Fil: Exposito, Veronica. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas; Argentina. Universidad de Tampere; FinlandiaFil: Pickard, Natasha. California State University; Estados UnidosFil: Solbakk, Anne-Kristin. University of Oslo; NoruegaFil: Ogawa, Keith H.. Saint Mary's College Of California; Estados UnidosFil: Knight, Robert T.. California State University; Estados UnidosFil: Hartikainen, Kaisa M.. Universidad de Tampere; Finlandi
Cavity-enhanced optical Hall effect in two-dimensional free charge carrier gases detected at terahertz frequencies
The effect of a tunable, externally coupled Fabry-P\'{e}rot cavity to
resonantly enhance the optical Hall effect signatures at terahertz frequencies
produced by a traditional Drude-like two-dimensional electron gas is shown and
discussed in this communication. As a result, the detection of optical Hall
effect signatures at conveniently obtainable magnetic fields, for example by
neodymium permanent magnets, is demonstrated. An AlInN/GaN-based high electron
mobility transistor structure grown on a sapphire substrate is used for the
experiment. The optical Hall effect signatures and their dispersions, which are
governed by the frequency and the reflectance minima and maxima of the
externally coupled Fabry-P\'{e}rot cavity, are presented and discussed. Tuning
the externally coupled Fabry-P\'{e}rot cavity strongly modifies the optical
Hall effect signatures, which provides a new degree of freedom for optical Hall
effect experiments in addition to frequency, angle of incidence and magnetic
field direction and strength
Self-intersection local time of planar Brownian motion based on a strong approximation by random walks
The main purpose of this work is to define planar self-intersection local
time by an alternative approach which is based on an almost sure pathwise
approximation of planar Brownian motion by simple, symmetric random walks. As a
result, Brownian self-intersection local time is obtained as an almost sure
limit of local averages of simple random walk self-intersection local times. An
important tool is a discrete version of the Tanaka--Rosen--Yor formula; the
continuous version of the formula is obtained as an almost sure limit of the
discrete version. The author hopes that this approach to self-intersection
local time is more transparent and elementary than other existing ones.Comment: 36 pages. A new part on renormalized self-intersection local time has
been added and several inaccuracies have been corrected. To appear in Journal
of Theoretical Probabilit
Stochastic integration based on simple, symmetric random walks
A new approach to stochastic integration is described, which is based on an
a.s. pathwise approximation of the integrator by simple, symmetric random
walks. Hopefully, this method is didactically more advantageous, more
transparent, and technically less demanding than other existing ones. In a
large part of the theory one has a.s. uniform convergence on compacts. In
particular, it gives a.s. convergence for the stochastic integral of a finite
variation function of the integrator, which is not c\`adl\`ag in general.Comment: 16 pages, some typos correcte
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Systemic 'biodiversity' governing
Stemming biodiversity loss requires taking responsibility for the quality and trajectory of unfolding socialbiosphere dynamics through transformations to systemic governance. Existing systems are woefully inadequate for the task at hand – from preferential lobbying by big business corrupting decision-making to conventional economics treating the ‘environment’ as an externality. Biodiversity will continue to decline without the reinvention of governance at all levels. We propose a new model through the addition of the ‘Biosphere’, ‘Technosphere’, and ‘Social Purpose’ to the contemporary governance model. This would place biosphere-human relations at its centre, with the invention and enactment of new institutions for social purpose, using expressions of democracy going far beyond electoral representation. Biodiversity conservation is dependent on co-design with local actors – it cannot succeed from a remote desk. In turn, this will mean taking responsibility for the framing choices applied to situations of concern as the first critical steps for thinking differently; incorporating multiple perspectives; and designing for purpose. Designed human activity systems to carry out these steps will come in many forms. All will need systemic sensibilities characterised by relational thinking and practice, investment in systems literacy and the deployment of STiP (systems thinking in practice) by co-designers and enactors of new governance systems
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