1,312 research outputs found
Sweet Nellie Bawn
https://digitalcommons.library.umaine.edu/mmb-vp/6612/thumbnail.jp
Plumage and ecology of cormorants
The paper draws on data attending the etho-ecology of four species of cormorants (Phalacrocoracidae) in support of an hypothesis for the adaptive significance of the predominantly dark plumage of these birds. It is suggested that a dark plumage, primarily by being most receptive to solar radiation, assists cormorants in supplementing metabolic heat for maintenance of normal body temperature. In those cormorants which have white extending over ventral and frontal aspects of the body, it is suggested that this is an adaptation to the feeding situation and that it promotes 'hunting camouflage' through countershading
Relativistic many-body calculations of electric-dipole matrix elements, lifetimes and polarizabilities in rubidium
Electric-dipole matrix elements for ns-n'p, nd-n'p, and 6d-4f transitions in
Rb are calculated using a relativistic all-order method. A third-order
calculation is also carried out for these matrix elements to evaluate the
importance of the high-order many-body perturbation theory contributions. The
all-order matrix elements are used to evaluate lifetimes of ns and np levels
with n=6, 7, 8 and nd levels with n=4, 5, 6 for comparison with experiment and
to provide benchmark values for these lifetimes. The dynamic polarizabilities
are calculated for ns states of rubidium. The resulting lifetime and
polarizability values are compared with available theory and experiment.Comment: 8 pages, 2 figure
Optimizing the fast Rydberg quantum gate
The fast phase gate scheme, in which the qubits are atoms confined in sites
of an optical lattice, and gate operations are mediated by excitation of
Rydberg states, was proposed by Jaksch et al. Phys. Rev. Lett. 85, 2208 (2000).
A potential source of decoherence in this system derives from motional heating,
which occurs if the ground and Rydberg states of the atom move in different
optical lattice potentials. We propose to minimize this effect by choosing the
lattice photon frequency \omega so that the ground and Rydberg states have the
same frequency-dependent polarizability \alpha(omega). The results are
presented for the case of Rb.Comment: 5 pages, submitted to PR
A 5˚C Arctic in a 2°C World. Challenges and recommendations for immediate action from the July 21-22, 2016 Workshop: Briefing Paper for Arctic Science Ministerial, September 20, 2016
The Columbia Climate Center, in partnership with World Wildlife Fund, Woods Hole Research Center, and Arctic 21, held a workshop titled A 5ËšC Arctic in a 2ËšC World on July 20 and 21, 2016.
The workshop was co-sponsored by the International Arctic Research Center (University of Alaska Fairbanks), the Arctic Institute of North America (Canada), the MEOPAR Network (Marine Environmental Observation, Prediction, and Response), and the Future Ocean Excellence Cluster.
The goal of the workshop was to advance thinking on the science and policy implications of the
temperature change in the context of the 1.5 to <2ËšC warming expected for the globe, as discussed during the 21st session of the Conference of the Parties of the United Nations Framework Convention on Climate Change at Paris in 2015. For the Arctic, such an increase means an anticipated increase of roughly 3.5 to 5ËšC. An international group of 41 experts shared perspectives on the regional and global impacts of an up to +5ËšC Arctic, examined the feasibility of actively lowering Arctic temperatures, and considered realistic timescales associated with such interventions.
The group also discussed the science and the political and governance actions required for
alternative Arctic futures
The MIDAS telescope for microwave detection of ultra-high energy cosmic rays
We present the design, implementation and data taking performance of the
MIcrowave Detection of Air Showers (MIDAS) experiment, a large field of view
imaging telescope designed to detect microwave radiation from extensive air
showers induced by ultra-high energy cosmic rays. This novel technique may
bring a tenfold increase in detector duty cycle when compared to the standard
fluorescence technique based on detection of ultraviolet photons. The MIDAS
telescope consists of a 4.5 m diameter dish with a 53-pixel receiver camera,
instrumented with feed horns operating in the commercial extended C-Band (3.4
-- 4.2 GHz). A self-trigger capability is implemented in the digital
electronics. The main objectives of this first prototype of the MIDAS telescope
- to validate the telescope design, and to demonstrate a large detector duty
cycle - were successfully accomplished in a dedicated data taking run at the
University of Chicago campus prior to installation at the Pierre Auger
Observatory.Comment: 13 pages, 18 figure
Constraining spacetime torsion with LAGEOS
We compute the corrections to the orbital Lense-Thirring effect (or
frame-dragging) in the presence of spacetime torsion. We derive the equations
of motion of a test body in the gravitational field of a rotating axisymmetric
massive body, using the parametrized framework of Mao, Tegmark, Guth and Cabi.
We calculate the secular variations of the longitudes of the node and of the
pericenter. We also show how the LAser GEOdynamics Satellites (LAGEOS) can be
used to constrain torsion parameters. We report the experimental constraints
obtained using both the nodes and perigee measurements of the orbital
Lense-Thirring effect. This makes LAGEOS and Gravity Probe B (GPB)
complementary frame-dragging and torsion experiments, since they constrain
three different combinations of torsion parameters
High-precision calculations of van der Waals coefficients for heteronuclear alkali-metal dimers
Van der Waals coefficients for the heteronuclear alkali-metal dimers of Li,
Na, K, Rb, Cs, and Fr are calculated using relativistic ab initio methods
augmented by high-precision experimental data. We argue that the uncertainties
in the coefficients are unlikely to exceed about 1%.Comment: 11 pages, 2 figs, graphicx.st
New method for true-triaxial rock testing
Two new and related true-triaxial apparatus are described that make use of conventional triaxial pressure vessels in combination with specially configured, high-pressure hydraulic jacks inside these vessels. The development combines advantages not found in existing facilities, including a compact design, pore-pressure and flow-through capabilities, the ability to attain high principal stresses and principal stress differences, direct access to parts of the sample, and provisions to go to relatively large deformations without developing serious stress field inhomogeneities
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