1,703 research outputs found
On Doppler tracking in cosmological spacetimes
We give a rigorous derivation of the general-relativistic formula for the
two-way Doppler tracking of a spacecraft in Friedmann-Lemaitre-Robertson-Walker
and in McVittie spacetimes. The leading order corrections of the so-determined
acceleration to the Newtonian acceleration are due to special-relativistic
effects and cosmological expansion. The latter, although linear in the Hubble
constant, is negligible in typical applications within the Solar System.Comment: 10 pages, 1 figure. Journal versio
Correlation between the rheology of 2D-inks precursors and the droplet size generated from a capillary nozzle in dripping regime
This study provides a complete rheological characterization of 2D
nanomaterial dispersions, employed as 2D-inks precursors in printed
electronics. Three different 2D nanomaterials (molybdenum disulfide (MoS2),
graphene, and hexagonal boron nitride(hBN)) were dispersed in a Newtonian fluid
(toluene) and a viscoelastic fluid (toluene + ethyl cellulose) with different
polymer concentrations. The presence of nanoparticles does not change the shear
rheology of the carrier fluid. Regarding the extensional rheology, the results
showed that the pinch-off phenomenon is present in all Toluene suspensions;
however, the presence of the ethyl cellulose introduces elasticity in the
system, even leading to the formation of beads-on-a-string, and the relaxation
times of the suspensions depends on the kind of nanoparticles present in the
fluid. As controlling the droplet size when dispensing 2D-inks is of paramount
importance for printed electronics, as well as for many other applications,
here it is presented a correlation between the rheological properties of these
2D-inks precursors and their droplet size when generated from a capillary
nozzle in dripping regime
Sensitivity and representativeness of One-Health surveillance for diseases of zoonotic potential at health facilities relative to household visits in rural Guatemala
Most human and animal disease notification systems are unintegrated and passive, resulting in underreporting. Active surveillance can complement passive efforts, but because they are resource-intensive, their attributes must be evaluated. We assessed the sensitivity and representativeness of One-Health surveillance conducted at health facilities compared to health facilities plus monthly household visits in three rural communities of Guatemala. From September 2017 to November 2018, we screened humans for acute diarrheal, febrile and respiratory infectious syndromes and canines, swine, equines and bovines for syndromic events or deaths. We estimated the relative sensitivity as the incidence rate ratio of detecting an event in health facility surveillance compared to household surveillance from Poisson models. We used interaction terms between the surveillance method and sociodemographic factors or time trends to assess effect modification as a measure of relative representativeness. We used generalized additive models with smoothing splines to model incidence over time by surveillance method. We randomized 216 households to health facility surveillance and 198 to health facility surveillance plus monthly household visits. Health facility surveillance alone was less sensitive than when combined with household surveillance by 0.42 (95% CI: 0.34, 0.53), 0.56 (95% CI: 0.39, 0.79), 0.02 (95% CI: 0.00, 0.10), 0.28 (95% CI: 0.15, 0.50) and 0.22 (95% CI: 0.03, 0.92) times for human acute infections, human severe acute infections, and deaths in canines, swine and equines, respectively. Health facility surveillance alone underrepresented Spanish speakers (interaction p-value = 0.0003) and persons in higher economic assets (interaction p-values = 0.0008). The trend in incidence over time was different between the two study groups, with a larger decrease in the group with household surveillance (all interaction p-values <0.10). Surveillance at health facilities under ascertains syndromes in humans and animals which leads to underestimation of the burden of zoonotic disease. The magnitude of under ascertainment was differentially by sociodemographic factors, yielding an unrepresentative sample of health events. However, it is less time-intensive, thus might be sustained over time longer than household surveillance. The choice between methodologies should be evaluated against surveillance goals and available resources
The Large Aperture GRB Observatory
The Large Aperture GRB Observatory (LAGO) is aiming at the detection of the
high energy (around 100 GeV) component of Gamma Ray Bursts, using the single
particle technique in arrays of Water Cherenkov Detectors (WCD) in high
mountain sites (Chacaltaya, Bolivia, 5300 m a.s.l., Pico Espejo, Venezuela,
4750 m a.s.l., Sierra Negra, Mexico, 4650 m a.s.l). WCD at high altitude offer
a unique possibility of detecting low gamma fluxes in the 10 GeV - 1 TeV range.
The status of the Observatory and data collected from 2007 to date will be
presented.Comment: 4 pages, proceeding of 31st ICRC 200
Water Cherenkov Detectors response to a Gamma Ray Burst in the Large Aperture GRB Observatory
In order to characterise the behaviour of Water Cherenkov Detectors (WCD)
under a sudden increase of 1 GeV - 1 TeV background photons from a Gamma Ray
Burst (GRB), simulations were conducted and compared to data acquired by the
WCD of the Large Aperture GRB Observatory (LAGO). The LAGO operates arrays of
WCD at high altitude to detect GRBs using the single particle technique. The
LAGO sensitivity to GRBs is derived from the reported simulations of the gamma
initiated particle showers in the atmosphere and the WCD response to
secondaries.Comment: 5 pages, proceeding of the 31st ICRC 200
The Pioneer anomaly in the context of the braneworld scenario
We examine the Pioneer anomaly - a reported anomalous acceleration affecting
the Pioneer 10/11, Galileo and Ulysses spacecrafts - in the context of a
braneworld scenario. We show that effects due to the radion field cannot
account for the anomaly, but that a scalar field with an appropriate potential
is able to explain the phenomena. Implications and features of our solution are
analyzed.Comment: Final version to appear at Classical & Quantum Gravity. Plainlatex 19
page
A Mission to Explore the Pioneer Anomaly
The Pioneer 10 and 11 spacecraft yielded the most precise navigation in deep
space to date. These spacecraft had exceptional acceleration sensitivity.
However, analysis of their radio-metric tracking data has consistently
indicated that at heliocentric distances of astronomical units,
the orbit determinations indicated the presence of a small, anomalous, Doppler
frequency drift. The drift is a blue-shift, uniformly changing with a rate of
Hz/s, which can be interpreted as a
constant sunward acceleration of each particular spacecraft of . This signal has become known as the Pioneer
anomaly. The inability to explain the anomalous behavior of the Pioneers with
conventional physics has contributed to growing discussion about its origin.
There is now an increasing number of proposals that attempt to explain the
anomaly outside conventional physics. This progress emphasizes the need for a
new experiment to explore the detected signal. Furthermore, the recent
extensive efforts led to the conclusion that only a dedicated experiment could
ultimately determine the nature of the found signal. We discuss the Pioneer
anomaly and present the next steps towards an understanding of its origin. We
specifically focus on the development of a mission to explore the Pioneer
Anomaly in a dedicated experiment conducted in deep space.Comment: 8 pages, 9 figures; invited talk given at the 2005 ESLAB Symposium
"Trends in Space Science and Cosmic Vision 2020", 19-21 April 2005, ESTEC,
Noordwijk, The Netherland
Cultivation of algae in photobioreator and obtention of biodiesel
In this work we described the cultivation of Chlorella vulgaris in a photobioreactor to algal biomass production. The dried biomass was used as feedstock for biodiesel production, it presented 26% lipids and via sonocatalysis stage of the methodology resulted in 60% of fatty acid methyl esters (FAME). The FAME content was confirmed by Gas Chromatography (GC).CNPqFAPERGSCoordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES
Synthesis of Non-uniformly Correlated Partially Coherent Sources Using a Deformable Mirror
The near real-time synthesis of a non-uniformly correlated partially coherent source using a low-actuator-count deformable mirror is demonstrated. The statistical optics theory underpinning the synthesis method is reviewed. The experimental results of a non-uniformly correlated source are presented and compared to theoretical predictions. A discussion on how deformable mirror characteristics such as actuator count and pitch affect source generation is also included
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