20,348 research outputs found
Editorial: Beyond Pythagoras
This fourth journal issue of Divergence Press is a selection of papers given at the Beyond Pythagoras Symposium held at the University of Huddersfield’s Centre for Research in New Music, 21-23 March 2014. The symposium sought to explore new trends in the sonic arts and experimental electronic music particularly new tuning systems, post-acousmatic and post-digital aesthetics, as well as the re-embodiment of sound production and listening
The hydrogen atom in dimensions
The nonrelativistic hydrogen atom in dimensions is the
reference system for perturbative schemes used in dimensionally regularized
nonrelativistic effective field theories to describe hydrogen-like atoms.
Solutions to the -dimensional Schr\"odinger-Coulomb equation are given in
the form of a double power series. Energies and normalization integrals are
obtained numerically and also perturbatively in terms of . The
utility of the series expansion is demonstrated by the calculation of the
divergent expectation value .Comment: 5 page
Virtual annihilation contribution to orthopositronium decay rate
Order alpha^2 contribution to the orthopositronium decay rate due to
one-photon virtual annihilation is found to be
delta Gamma = (alpha/pi)^2 (pi^2 ln(alpha) - 0.8622(9))Gamma_LO.Comment: 2 pages, no figure
Irrational constants in positronium decays
We establish irrational constants, that contribute to the positronium
lifetime at and order. In particular we show, that a
new type of constants appear, which are not related to Euler--Zagier sums or
multiple values.Comment: Presented at 9th Workshop on Elementary Particle Theory: Loops and
Legs in Quantum Field Theory, Sondershausen, 20-25 Apr 2008. 6 pages, 3
figure
The vertical distribution of iron stable isotopes in the North Atlantic near Bermuda
Seawater dissolved iron isotope ratios (δ^(56)Fe) have been measured in the North Atlantic near Bermuda. In a full-depth profile, seawater dissolved δ^(56)Fe is isotopically heavy compared to crustal values throughout the water column (δ^(56)Fe_(IRMM-014) = +0.30‰ to +0.71‰). Iron isotope ratios are relatively homogenous in the upper water column (between +0.30‰ to +0.45‰ above 1500 m), and δ^(56)Fe increases below this to a maximum of +0.71‰ at 2500 m, decreasing again to +0.35‰ at 4200 m. The δ^(56)Fe profile is very different from the iron concentration profile; in the upper water column [Fe] is variable while δ^(56)Fe is relatively constant, and in the deeper water column δ^(56)Fe varies while [Fe] remains relatively constant. The δ^(56)Fe profile is also not well correlated with other hydrographic tracers in the North Atlantic such as temperature, salinity, or the concentrations of oxygen, phosphate, silica, and CFC-11. The dissimilarity between δ^(56)Fe profiles and profiles of [Fe] and other hydrographic tracers shows that Fe isotope ratios provide a unique sort of information about ocean chemistry, and they suggest that Fe isotopes may therefore be a valuable new tool for tracing the global sources, sinks, and biogeochemical cycling of Fe
The Global Food Security Act: America\u27s Strategic Approach to Combating World Hunger
The world’s farms currently produce enough calories to adequately feed everyone on the planet. From the 1960s through 2008, per capita food availability worldwide has risen from 2220 kilocalories per person per day to 2790. Specifically, developing countries have recorded a rise in kilocalories per person per day, from 1850 to 2640. Yet, despite overall availability, around 815 million people still suffer from hunger or some form of malnutrition. Approximately one in ten people are undernourished
Changing atmospheric Δ^(14)C and the record of deep water paleoventilation ages
We propose a new calculation method to better estimate the deep water ventilation age from benthic-planktonic foraminifera ^(14)C ages. Our study is motivated by the fact that changes in atmospheric Δ^(14)C through time can cause contemporary benthic and planktonic foraminifera to have different initial Δ^(14)C values. This effect can cause spurious ventilation age changes to be interpreted from the geologic data. Using a new calculation method, ^(14)C projection ages, we recalculate the data from the Pacific Ocean. Contrary to previous results, we find that the Pacific intermediate and deep waters were about 600 years older than today at the last glacial maximum. In addition, there are possible signals of ventilation age change prior to ice sheet melting and at the Younger Dryas. However, the data are still too sparse to constrain these ventilation transients
Automatic sample rotator for metallographic polishing
Simple, inexpensive device can be attached to most metallographic sample polishing tables. It provides a suitable surface finish for microscopic examination or photography of surface details of the samples
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