4,110 research outputs found
Repeat-Accumulate Codes for Reconciliation in Continuous Variable Quantum Key Distribution
This paper investigates the design of low-complexity error correction codes
for the verification step in continuous variable quantum key distribution
(CVQKD) systems. We design new coding schemes based on quasi-cyclic
repeat-accumulate codes which demonstrate good performances for CVQKD
reconciliation
Resonance-continuum interference in the di-photon Higgs signal at the LHC
A low mass Standard Model Higgs boson should be visible at the Large Hadron
Collider through its production via gluon-gluon fusion and its decay to two
photons. We compute the interference of this resonant process, gg -> H -> gamma
gamma, with the continuum QCD background, gg -> gamma gamma induced by quark
loops. Helicity selection rules suppress the effect, which is dominantly due to
the imaginary part of the two-loop gg -> gamma gamma scattering amplitude. The
interference is destructive, but only of order 5% in the Standard Model, which
is still below the 10-20% present accuracy of the total cross section
prediction. We comment on the potential size of such effects in other Higgs
models.Comment: 10 pages, 2 figure
Ethanol Plant Location Determinants and County Comparative Advantage
The location of ethanol plants is determined by infrastructure, product and input markets, fiscal attributes of local communities, and state and federal incentives. This empirical analysis uses probit regression along with spatial clustering methods to analyze investment activity of ethanol plants at the county level for the lower U.S. 48 states from 2000 to 2007. The availability of feedstock dominates the site selection decision. Other factors, such as access to navigable rivers or railroads, product markets, producer credit and excise tax exemptions, and methyl tertiary-butyl ether bans provided some counties with a comparative advantage in attracting ethanol plants.cluster analysis, comparative advantage, ethanol production, location model, Community/Rural/Urban Development, Environmental Economics and Policy, Political Economy, R1, R3,
Capabilities of Earth-based radar facilities for near-Earth asteroid observations
We evaluated the planetary radar capabilities at Arecibo, the Goldstone 70-m
DSS-14 and 34-m DSS-13 antennas, the 70-m DSS-43 antenna at Canberra, the Green
Bank Telescope, and the Parkes Radio Telescope in terms of their relative
sensitivities and the number of known near-Earth asteroids (NEAs) detectable
per year in monostatic and bistatic configurations. In the 2015 calendar year,
monostatic observations with Arecibo and DSS-14 were capable of detecting 253
and 131 NEAs respectively, with signal-to-noise ratios (SNRs) greater than
30/track. Combined, the two observatories were capable of detecting 276 NEAs.
Of these, Arecibo detected 77 and Goldstone detected 32, or 30% and 24% the
numbers that were possible. The two observatories detected an additional 18 and
7 NEAs respectively, with SNRs of less than 30/track. This indicates that a
substantial number of potential targets are not being observed. The bistatic
configuration with DSS-14 transmitting and the Green Bank Telescope receiving
was capable of detecting about 195 NEAs, or ~50% more than with monostatic
observations at DSS-14. Most of the detectable asteroids were targets of
opportunity that were discovered less than 15 days before the end of their
observing windows. About 50% of the detectable asteroids have absolute
magnitudes > 25, which corresponds diameters < ~30 m.Comment: 12 pages, 7 figures, Accepted to A
Hoplopleura janzeni n. sp. (Phthiraptera: Anoplura), a new sucking louse from a Central American swimming mouse
Both sexes of a new species of sucking louse Hoplopleura janzeni (Phthiraptera: Hoplopleuridae) are described and illustrated from the Central American ichthyomyine swimming mouse Rheomys raptor (Rodentia: Muridae) collected in Costa Rica. The morphology of the new species is compared with that of Hoplopleura exima Johnson, the only other species of sucking louse known to parasitize an ichthyomyine rodent. Hoplopleura janzeni is unique in having posteriorly directed spurs on the first antennal segment, the fore- and midcoxae, and the hind femora of both sexes
An Experimental Investigation of Helicopter Rotor Hub Fairing Drag Characteristics
A study was done in the NASA 14- by 22-Foot Wind Tunnel at Langley Research Center on the parasite drag of different helicopter rotor hub fairings and pylons. Parametric studies of hub-fairing camber and diameter were conducted. The effect of hub fairing/pylon clearance on hub fairing/pylon mutual interference drag was examined in detail. Force and moment data are presented in tabular and graphical forms. The results indicate that hub fairings with a circular-arc upper surface and a flat lower surface yield maximum hub drag reduction; and clearance between the hub fairing and pylon induces high mutual-interference drag and diminishes the drag-reduction benefit obtained using a hub fairing with a flat lower surface. Test data show that symmetrical hub fairings with circular-arc surfaces generate 74 percent more interference drag than do cambered hub fairings with flat lower surfaces, at moderate negative angle of attack
Imaging a single atom in a time-of-flight experiment
We perform fluorescence imaging of a single 87Rb atom after its release from
an optical dipole trap. The time-of-flight expansion of the atomic spatial
density distribution is observed by accumulating many single atom images. The
position of the atom is revealed with a spatial resolution close to 1
micrometer by a single photon event, induced by a short resonant probe. The
expansion yields a measure of the temperature of a single atom, which is in
very good agreement with the value obtained by an independent measurement based
on a release-and-recapture method. The analysis presented in this paper
provides a way of calibrating an imaging system useful for experimental studies
involving a few atoms confined in a dipole trap.Comment: 14 pages, 8 figure
Energy distribution and cooling of a single atom in an optical tweezer
We investigate experimentally the energy distribution of a single rubidium
atom trapped in a strongly focused dipole trap under various cooling regimes.
Using two different methods to measure the mean energy of the atom, we show
that the energy distribution of the radiatively cooled atom is close to
thermal. We then demonstrate how to reduce the energy of the single atom, first
by adiabatic cooling, and then by truncating the Boltzmann distribution of the
single atom. This provides a non-deterministic way to prepare atoms at low
microKelvin temperatures, close to the ground state of the trapping potential.Comment: 9 pages, 6 figures, published in PR
- …