2,806 research outputs found
Interacting dark sector with variable vacuum energy
We examine a cosmological scenario where dark matter is coupled to a variable
vacuum energy while baryons and photons are two decoupled components for a
spatially flat Friedmann-Robertson-Walker spacetime. We apply the
method to the updated observational Hubble data for constraining the
cosmological parameters and analyze the amount of dark energy in the radiation
era. We show that our model fulfills the severe bound of at the level, so it is consistent with the recent
analysis that includes cosmic microwave background anisotropy measurements from
the Planck survey, the Atacama Cosmology Telescope, and the South Pole
Telescope along with the future constraints achievable by the Euclid and CMBPol
experiments, and fulfills the stringent bound at the level in the big-bang nucleosynthesis epoch.Comment: 5 pages,3 figures, 2 tables.
(http://prd.aps.org/abstract/PRD/v88/i8/e087301
Full two-photon downconversion of just a single photon
We demonstrate, both numerically and analytically, that it is possible to
generate two photons from one and only one photon. We characterize the output
two photon field and make our calculations close to reality by including
losses. Our proposal relies on real or artificial three-level atoms with a
cyclic transition strongly coupled to a one-dimensional waveguide. We show that
close to perfect downconversion with efficiency over 99% is reachable using
state-of-the-art Waveguide QED architectures such as photonic crystals or
superconducting circuits. In particular, we sketch an implementation in circuit
QED, where the three level atom is a transmon
Effect of the nature of exogenous organic matter on pesticide sorption by the soil
A study was carried out on the sorption of two sparingly water-soluble pesticides (diazinon and linuron) by a sandy loam soil modified with different exogenous organic materials (EOMs) containing humic like substances: city refuse compost (CRC), peat (P), commercial humic acid (HA), liquid humic acid (LHA) extracted from leonardite and two (non humic) model compounds (surfactants): tetradecyltrimethylammonium bromide (TDTMA) and sodium dodecyl sulphate (SDS) before and after 2 and 8 months incubation periods with the soil.
In all cases, the isotherms fitted the Freundlich sorption equation (x/m=KCen), generally with r2 values greater than 0.99. The value of the sorption constant K for the natural soil was 8.81 for diazinon and 2.29 for linuron. These values increased significantly for EOM modified soils with respect to natural soil, with the exception of the samples modified with SDS and LHA, in which cases they decreased, possibly due to the micellar properties of these compounds. Incubation of EOMs with soil increased their sorption capacity: the Koc values were increased proportionally to the incubation time for both pesticides and for all treatments carried out. Accordingly, the sorption capacity of hydrophobic pesticides increases with the degree of evolution in the soil of EOMs with humic type compounds, possibly due, among other causes, to the increase in the EOMs colloidal properties and the modifications occurring in the hydrophobic- hydrophilic characteristics of the soil surfaces.
The main conclusion is that application to the soil of solid carbon rich wastes, especially those with a high degree of maturity, may offer an important strategy for reducing pesticide leaching, and for eliminating pesticide residues from soil with the use of liquid humic acids.Peer reviewe
Effect of the nature of exogenous organic matter on pesticide sorption by the soil
A study was carried out on the sorption of two sparingly water-soluble pesticides (diazinon and linuron) by a sandy loam soil modified with different exogenous organic materials (EOMs) containing humic like substances: city refuse compost (CRC), peat (P), commercial humic acid (HA), liquid humic acid (LHA) extracted from leonardite and two (non humic) model compounds (surfactants): tetradecyltrimethylammonium bromide (TDTMA) and sodium dodecyl sulphate (SDS) before and after 2 and 8 months incubation periods with the soil.
In all cases, the isotherms fitted the Freundlich sorption equation (x/m=KCen), generally with r2 values greater than 0.99. The value of the sorption constant K for the natural soil was 8.81 for diazinon and 2.29 for linuron. These values increased significantly for EOM modified soils with respect to natural soil, with the exception of the samples modified with SDS and LHA, in which cases they decreased, possibly due to the micellar properties of these compounds. Incubation of EOMs with soil increased their sorption capacity: the Koc values were increased proportionally to the incubation time for both pesticides and for all treatments carried out. Accordingly, the sorption capacity of hydrophobic pesticides increases with the degree of evolution in the soil of EOMs with humic type compounds, possibly due, among other causes, to the increase in the EOMs colloidal properties and the modifications occurring in the hydrophobic- hydrophilic characteristics of the soil surfaces.
The main conclusion is that application to the soil of solid carbon rich wastes, especially those with a high degree of maturity, may offer an important strategy for reducing pesticide leaching, and for eliminating pesticide residues from soil with the use of liquid humic acids.Peer reviewe
A Mathematical Model to Study the Meningococcal Meningitis
AbstractThe main goal of this work is to introduce a novel mathematical model to study the spreading of meningococcal meningitis. Specifically, it is a discrete mathematical model based on cellular automata where the population is divided in five classes: sus- ceptible, asymptomatic infected, infected with symptoms, carriers, recovered and died. It catches the individual characteristics of people in order to give a prediction of both the individual behavior, and whole evolution of population
Effects of introgressed 4Nv Aegilops ventricosa chromosome on yield and yield components in bread wheat.
Effects of introgressed 4Nv Aegilops ventricosa chromosome on yield and yield components in bread whea
Local and average fields inside surface-disordered waveguides: Resonances in the one-dimensional Anderson localization regime
We investigate the one-dimensional propagation of waves in the Anderson
localization regime, for a single-mode, surface disordered waveguide. We make
use of both an analytical formulation and rigorous numerical simulation
calculations. The occurrence of anomalously large transmission coefficients for
given realizations and/or frequencies is studied, revealing huge field
intensity concentration inside the disordered waveguide. The analytically
predicted s-like dependence of the average intensity, being in good agreement
with the numerical results for moderately long systems, fails to explain the
intensity distribution observed deep in the localized regime. The average
contribution to the field intensity from the resonances that are above a
threshold transmission coefficient is a broad distribution with a large
maximum at/near mid-waveguide, depending universally (for given ) on the
ratio of the length of the disorder segment to the localization length,
. The same universality is observed in the spatial distribution of the
intensity inside typical (non-resonant with respect to the transmission
coefficient) realizations, presenting a s-like shape similar to that of the
total average intensity for close to 1, which decays faster the lower
is . Evidence is given of the self-averaging nature of the random
quantity . Higher-order moments of the intensity are
also shown.Comment: 9 pages, 9 figure
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