14,706 research outputs found
Oil Prices and the Impact of Rising Economies
•The first commercial oil well was drilled in Romania in 1857, since then oil has been playing a crucial role in the global economy. •High oil prices can slow economic growth, cause inflationary pressures and create global imbalances. •High oil prices and tight market conditions have also raised fears about oil scarcity and concerns about energy security in many oil- importing countries. •The supply-demand factor seems to be popular among the factors that outweigh the impact of Organization of Petroleum Exporting Countries (OPEC)
Current-induced reversal in magnetic nanopillars passivated by silicon
We demonstrate that magnetic multilayer nanopillars can be efficiently
protected from oxidation by coating with silicon. Both the protected and the
oxidized nanopillars exhibit an increase of reversal current at cryogenic
temperatures. However the magnetic excitation onset current increases only in
the oxidized samples. We show that oxidized nanopillars exhibit anomalous
switching statistics at low temperature, providing a simple test for the
quality of magnetic nanodevices.Comment: 3 pages, 4 figure
Cross-Entropy Clustering
We construct a cross-entropy clustering (CEC) theory which finds the optimal
number of clusters by automatically removing groups which carry no information.
Moreover, our theory gives simple and efficient criterion to verify cluster
validity.
Although CEC can be build on an arbitrary family of densities, in the most
important case of Gaussian CEC:
{\em -- the division into clusters is affine invariant;
-- the clustering will have the tendency to divide the data into
ellipsoid-type shapes;
-- the approach is computationally efficient as we can apply Hartigan
approach.}
We study also with particular attention clustering based on the Spherical
Gaussian densities and that of Gaussian densities with covariance s \I. In
the letter case we show that with converging to zero we obtain the
classical k-means clustering
Bayesian Learning Models of Pain: A Call to Action
Learning is fundamentally about action, enabling the successful navigation of a changing and uncertain environment. The experience of pain is central to this process, indicating the need for a change in action so as to mitigate potential threat to bodily integrity. This review considers the application of Bayesian models of learning in pain that inherently accommodate uncertainty and action, which, we shall propose are essential in understanding learning in both acute and persistent cases of pain
Spontaneous rotational inversion in Phycomyces
The filamentary fungus Phycomyces blakesleeanus undergoes a series of remarkable transitions during aerial growth. During what is known as the Stage IV growth phase, the fungus extends while rotating in a counterclockwise manner when viewed from above (Stage IVa) and then, while continuing to grow, spontaneously reverses to a clockwise rotation (Stage IVb). This phase lasts for 24 - 48 hours and is sometimes followed by yet another reversal (Stage IVc) before the overall growth ends. Here, we propose a continuum mechanical model of this entire process using nonlinear, anisotropic, elasticity and show how helical anisotropy associated with the cell wall structure can induce spontaneous rotation and, under appropriate circumstances, the observed reversal of rotational handedness
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