546 research outputs found
Oceanography using remote sensors Status report, 1 Sep. 1967 - 1 Jan. 1968
Aircraft and spacecraft remote sensing of oceanographic features and interpretation of photography taken during Apollo 501 missio
Dynamic structure factor of Luttinger liquids with quadratic energy dispersion and long-range interactions
We calculate the dynamic structure factor S (omega, q) of spinless fermions
in one dimension with quadratic energy dispersion k^2/2m and long range
density-density interaction whose Fourier transform f_q is dominated by small
momentum-transfers q << q_0 << k_F. Here q_0 is a momentum-transfer cutoff and
k_F is the Fermi momentum. Using functional bosonization and the known
properties of symmetrized closed fermion loops, we obtain an expansion of the
inverse irreducible polarization to second order in the small parameter q_0 /
k_F. In contrast to perturbation theory based on conventional bosonization, our
functional bosonization approach is not plagued by mass-shell singularities.
For interactions which can be expanded as f_q = f_0 + f_0^{2} q^2/2 + O (q^4)
with finite f_0^{2} we show that the momentum scale q_c = 1/ | m f_0^{2} |
separates two regimes characterized by a different q-dependence of the width
gamma_q of the collective zero sound mode and other features of S (omega, q).
For q_c << q << k_F we find that the line-shape in this regime is
non-Lorentzian with an overall width gamma_q of order q^3/(m q_c) and a
threshold singularity at the lower edge.Comment: 33 Revtex pages, 17 figure
Self-consistent Overhauser model for the pair distribution function of an electron gas at finite temperature
We present calculations of the spin-averaged pair distribution function
in a homogeneous gas of electrons moving in dimensionality D=3 or D=2 at
finite temperature. The model involves the solution of a two-electron
scattering problem via an effective potential which embodies many-body effects
through a self-consistent Hartree approximation, leading to two-body wave
functions to be averaged over a temperature-dependent distribution of relative
momentum for electron pairs. We report illustrative numerical results for
in an intermediate-coupling regime and interpret them in terms of
changes of short-range order with increasing temperature.Comment: 6 pages, 5 figures, submitted to Solid State Communication
Fate of eprinomectin in goat milk and cheeses with different ripening times following pour-on administration
The distribution of eprinomectin in goat milk and cheeses (cacioricotta, caciotta, caprilisco) with different ripening times following a pour-on administration at a single dose rate (500 microg/kg of body weight) and a double dose rate (1,000 microg/kg of body weight) to goats with naturally occurring infections of gastrointestinal nematodes was studied. Milk residues of eprinomectin reached a maximum of 0.55+/-0.18 microg/kg and 1.70+/-0.31 microg/kg at the single and double doses, respectively. The drug concentrations decreased progressively until the fifth day after treatment, when they were less than the detection limit at both dose rates. The eprinomectin levels measured in all cheese types (both treatments) were higher than those recovered in milk at all the sampling times. In caciotta cheeses, the eprinomectin residues levels were constantly higher than other cheeses. With the exception of cheeses made with milk the first day after treatment, eprinomectin concentrations were nearly constant up to the fourth day then decreased by the fifth and sixth days after treatment. In all cases, at both the single and double dosages, the maximum level of eprinomectin residues in goat milk and cheeses remained below the maximum residual level of 20 microg/liter permitted for lactating cattle
Suppression of a Field Population of Aedes aegypti in Brazil by Sustained Release of Transgenic Male Mosquitoes
The increasing burden of dengue, and the relative failure of traditional vector control programs highlight the need to develop new control methods. SIT using self-limiting genetic technology is one such promising method. A self-limiting strain of Aedes aegypti, OX513A, has already reached the stage of field evaluation. Sustained releases of OX513A Ae. aegypti males led to 80% suppression of a target wild Ae. aegypti population in the Cayman Islands in 2010. Here we describe sustained series of field releases of OX513A Ae. aegypti males in a suburb of Juazeiro, Bahia, Brazil. This study spanned over a year and reduced the local Ae. aegypti population by 95% (95% CI: 92.2%-97.5%) based on adult trap data and 81% (95% CI: 74.9-85.2%) based on ovitrap indices compared to the adjacent no-release control area. The mating competitiveness of the released males (0.031; 95% CI: 0.025-0.036) was similar to that estimated in the Cayman trials (0.059; 95% CI: 0.011-0.210), indicating that environmental and target-strain differences had little impact on the mating success of the OX513A males. We conclude that sustained release of OX513A males may be an effective and widely useful method for suppression of the key dengue vector Ae. aegypti. The observed level of suppression would likely be sufficient to prevent dengue epidemics in the locality tested and other areas with similar or lower transmission
Pair densities at contact in the quantum electron gas
The value of the pair distribution function g(r) at contact (r = 0) in a
quantum electron gas is determined by the scattering events between pairs of
electrons with antiparallel spins. The theoretical results for g(0) as a
function of the coupling strength r_s in the paramagnetic electron gas in
dimensionality D=2 and 3, that have been obtained from the solution of the
two-body scattering problem with a variety of effective scattering potentials
embodying many-body effects, are compared with the results of many-body
calculations in the ladder approximation and with quantum Monte Carlo data.Comment: 7 pages, 2 figure
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