31,558 research outputs found
Phase Coherence in Multiple Pulse Optical Spectroscopy
In this paper we describe a new technique for the generation of multiple pulse phase coherent sequences in optical spectroscopy. The technique is an extension of the acousto-optic modulation and fluorescence detection methods developed for optical transitions by Zewail and Orlowski (Zewail et al., Chem. Phys. Lett. 48, 256 (1977); Orlowski et al., Chem. Phys. Lett. 54, 197 (1978)). Application of these multiple pulse trains (of different phases) to optical transitions of two-level and multilevel systems is demonstrated experimentally. It is shown that they can be used to (i) suppress spontaneous emission background, (ii) enhance coherent transients such as photon echoes, (iii) measure additional relaxation parameters in systems with complex rotational-vibrational levels, and (iv) enhance the effective laser bandwidths through composite pulse trains, as demonstrated on I2 gas. Finally, the potential of this development is extended to the possibility of observing selective multiquantum excitation in molecules
1-Click Energy: Managing Corporate Demand for Clean Power
Globally, more private businesses, especially Fortune 100 companies are generating their own electricity, investing in renewable energy facilities, and voluntarily purchasing renewable energy credits to cover their carbon footprints. This shift could have a significant impact on the existing energy delivery system. On the one hand, this shift shows positive momentum toward the incorporation of clean energy into a fossil fuel dominated grid. As the negative impacts of climate change accelerate around the globe, decreasing reliance on fossil fuels is certainly an important goal. On the other hand, corporate disruption of what has historically been a highly regulated public service industry could result in a slippery slope of market power and loosened consumer protections, lost profits and stranded costs for utilities, and increased utility bills for the remaining customers. This Article recommends changes to the current regulatory scheme that would (1) go further to protect customers from multinational corporate wholesale sellers of electricity and (2) allow utilities to plan and collaborate earlier with large corporate customers to meet their clean energy demands
2HOT: An Improved Parallel Hashed Oct-Tree N-Body Algorithm for Cosmological Simulation
We report on improvements made over the past two decades to our adaptive
treecode N-body method (HOT). A mathematical and computational approach to the
cosmological N-body problem is described, with performance and scalability
measured up to 256k () processors. We present error analysis and
scientific application results from a series of more than ten 69 billion
() particle cosmological simulations, accounting for
floating point operations. These results include the first simulations using
the new constraints on the standard model of cosmology from the Planck
satellite. Our simulations set a new standard for accuracy and scientific
throughput, while meeting or exceeding the computational efficiency of the
latest generation of hybrid TreePM N-body methods.Comment: 12 pages, 8 figures, 77 references; To appear in Proceedings of SC
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The Einstein Ring 0047-2808 Revisited: A Bayesian Inversion
In a previous paper, we outlined a new Bayesian method for inferring the
properties of extended gravitational lenses, given data in the form of resolved
images. This method holds the most promise for optimally extracting information
from the observed image, whilst providing reliable uncertainties in all
parameters. Here, we apply the method to the well studied optical Einstein ring
0047-2808. Our results are in broad agreement with previous studies, showing
that the density profile of the lensing galaxy is aligned within a few degrees
of the light profile, and suggesting that the source galaxy (at redshift 3.6)
is a binary system, although its size is only of order 1-2 kpc. We also find
that the mass of the elliptical lensing galaxy enclosed by the image is
(2.910.01) M_{\sun}. Our method is able to achieve
improved resolution for the source reconstructions, although we also find that
some of the uncertainties are greater than has been found in previous analyses,
due to the inclusion of extra pixels and a more general lens model.Comment: Accepted for publication in Ap
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