3,885 research outputs found
Binding energy of localized biexcitons in quantum wells
A variational calculation of the ground state energy of a biexciton in a
GaAs/AlGaAs quantum well is presented. The well width fluctuations leading to
trapping of the biexcitons are modeled by a parabolic potential. The results
obtained for different well widths are compared with recent experimental data.
Good agreement is obtained both for the biexciton binding energy and for the
Haynes factor. We find that the structure of a biexciton is similar to the one
of the H_2 molecule.Comment: 9 pages, 4 figure
Sea state monitoring using coastal GNSS-R
We report on a coastal experiment to study GPS L1 reflections. The campaign
was carried out at the Barcelona Port breaker and dedicated to the development
of sea-state retrieval algorithms. An experimental system built for this
purpose collected and processed GPS data to automatically generate a times
series of the interferometric complex field (ICF). The ICF was analyzed off
line and compared to a simple developed model that relates ICF coherence time
to the ratio of significant wave height (SWH) and mean wave period (MWP). The
analysis using this model showed good consistency between the ICF coherence
time and nearby oceanographic buoy data. Based on this result, preliminary
conclusions are drawn on the potential of coastal GNSS-R for sea state
monitoring using semi-empirical modeling to relate GNSS-R ICF coherence time to
SWH.Comment: All Starlab authors have contributed significantly; the Starlab
author list has been ordered randomly. Submitted to GR
The Eddy Experiment: accurate GNSS-R ocean altimetry from low altitude aircraft
During the Eddy Experiment, two synchronous GPS receivers were flown at 1 km
altitude to collect L1 signals and their reflections from the sea surface for
assessment of altimetric precision and accuracy. Wind speed (U10) was around 10
m/s, and SWH up to 2 m. A geophysical parametric waveform model was used for
retracking and estimation of the lapse between the direct and reflected signals
with a 1-second precision of 3 m. The lapse was used to estimate the SSH along
the track using a differential model. The RMS error of the 20 km averaged
GNSS-R absolute altimetric solution with respect to Jason-1 SSH and a GPS buoy
measurement was of 10 cm, with a 2 cm mean difference. Multipath and retracking
parameter sensitivity due to the low altitude are suspected to have degraded
accuracy. This result provides an important milestone on the road to a GNSS-R
mesoscale altimetry space mission.Comment: All Starlab authors have contributed significantly; the Starlab
Author list has been ordered randoml
Knowledge-Attitudes-Practices About Malaria Among Communities in Southern Benin
Malaria still remains the main public health problem in Benin. We explored the determinants that influenced malaria treatment as well as protective behaviors, to generate a framework of useful ideas as alternative strategies against malaria. A cross-sectional survey of the knowledge, attitudes and practices (KAP) was conducted at Hozin, Vakon and Agblangandan districts in southern region of Benin. Descriptive statistics were computed and mixed logistic regression helped evaluating the relationship between frequency of each category of severity of malaria and sex group, educational level, treatment, means of self-protection against mosquitoes and identification of the cause of malaria. A significant proportion 750 (81.3%) (p<0.001) of participants stated that malaria was caused by mosquitoes. The respondents who mentioned sun as the cause of malaria, have trivialized more malaria in a proportion of about 59.30% (OR=2.67 [95% CI 1.61-4.44]) followed by those who have reported the cause of body weakness (43.68%) (OR=2.97 [95% CI 1.68-5.28]). Poor knowledge justifies the trivialization of the disease and poor management of malaria control means. National Malaria Control Programs should improve access to education, especially for women and could help improving prevention and control behaviours against malaria in communities
- …